wroclaw-git-backups/nix
1
0
Fork 0
mirror of https://github.com/NixOS/nix synced 2025-07-10 04:43:53 +02:00
Code Activity

Tagging release 2.26.2

Browse source 
-----BEGIN PGP SIGNATURE-----
 
 iQFHBAABCAAxFiEEtUHVUwEnDgvPFcpdgXC0cm1xmN4FAmetA5oTHGVkb2xzdHJh
 QGdtYWlsLmNvbQAKCRCBcLRybXGY3g2pB/9JAFyjmaXuccbMTO/6x9qwsWuuXNLk
 OQWzfbdUekvsihZZSFZg1r7KqqXHCi64f0nxLPsJ/0oeDWZktJ5KnbV630nuUlDj
 ulLCpKdvhWFa8dVx9LiziGwQw4KLx8PjOfwThtQ4DqCWxWEmu6lKkijag9cE+ai4
 3mw9YtUjBRxlXyhYLzWz3whLbv37c/m+R8iGS8xm8W260pmei6D0beOIPdfXYBQF
 PzPlPORyI08A06uqyA3z7bTxzmSMnzvu0QInCPCKSHzFUnTZPHUYuYStFl28NrZS
 fXKK59L0G7QEfdTRAmqQkdHdtPj2RlYFiMN0kQiNLflvKfGGWdi/kvdx
 =rRix
 -----END PGP SIGNATURE-----

Merge tag '2.26.2' into sync-2.26.2

Tagging release 2.26.2
This commit is contained in:
Eelco Dolstra 2025-02-18 19:56:22 +01:00
commit 4055239936
1395 changed files with 24694 additions and 16040 deletions
Download patch file Download diff file Expand all files Collapse all files

193
doc/manual/source/SUMMARY.md.in Normal file
View file

@ -0,0 +1,193 @@
# Table of Contents
- [Introduction](introduction.md)
- [Quick Start](quick-start.md)
- [Installation](installation/index.md)
- [Supported Platforms](installation/supported-platforms.md)
- [Installing a Binary Distribution](installation/installing-binary.md)
- [Installing Nix from Source](installation/installing-source.md)
- [Prerequisites](installation/prerequisites-source.md)
- [Obtaining a Source Distribution](installation/obtaining-source.md)
- [Building Nix from Source](installation/building-source.md)
- [Using Nix within Docker](installation/installing-docker.md)
- [Security](installation/nix-security.md)
- [Single-User Mode](installation/single-user.md)
- [Multi-User Mode](installation/multi-user.md)
- [Environment Variables](installation/env-variables.md)
- [Upgrading Nix](installation/upgrading.md)
- [Uninstalling Nix](installation/uninstall.md)
- [Nix Store](store/index.md)
- [File System Object](store/file-system-object.md)
- [Content-Addressing File System Objects](store/file-system-object/content-address.md)
- [Store Object](store/store-object.md)
- [Content-Addressing Store Objects](store/store-object/content-address.md)
- [Store Path](store/store-path.md)
- [Store Types](store/types/index.md)
{{#include ./store/types/SUMMARY.md}}
- [Nix Language](language/index.md)
- [Data Types](language/types.md)
- [String context](language/string-context.md)
- [Syntax and semantics](language/syntax.md)
- [Variables](language/variables.md)
- [String literals](language/string-literals.md)
- [Identifiers](language/identifiers.md)
- [Scoping rules](language/scope.md)
- [String interpolation](language/string-interpolation.md)
- [Lookup path](language/constructs/lookup-path.md)
- [Operators](language/operators.md)
- [Built-ins](language/builtins.md)
- [Derivations](language/derivations.md)
- [Advanced Attributes](language/advanced-attributes.md)
- [Import From Derivation](language/import-from-derivation.md)
- [Package Management](package-management/index.md)
- [Profiles](package-management/profiles.md)
- [Garbage Collection](package-management/garbage-collection.md)
- [Garbage Collector Roots](package-management/garbage-collector-roots.md)
- [Advanced Topics](advanced-topics/index.md)
- [Sharing Packages Between Machines](package-management/sharing-packages.md)
- [Serving a Nix store via HTTP](package-management/binary-cache-substituter.md)
- [Serving a Nix store via SSH](package-management/ssh-substituter.md)
- [Remote Builds](advanced-topics/distributed-builds.md)
- [Tuning Cores and Jobs](advanced-topics/cores-vs-jobs.md)
- [Verifying Build Reproducibility](advanced-topics/diff-hook.md)
- [Using the `post-build-hook`](advanced-topics/post-build-hook.md)
- [Command Reference](command-ref/index.md)
- [Common Options](command-ref/opt-common.md)
- [Common Environment Variables](command-ref/env-common.md)
- [Main Commands](command-ref/main-commands.md)
- [nix-build](command-ref/nix-build.md)
- [nix-shell](command-ref/nix-shell.md)
- [nix-store](command-ref/nix-store.md)
- [nix-store --add-fixed](command-ref/nix-store/add-fixed.md)
- [nix-store --add](command-ref/nix-store/add.md)
- [nix-store --delete](command-ref/nix-store/delete.md)
- [nix-store --dump-db](command-ref/nix-store/dump-db.md)
- [nix-store --dump](command-ref/nix-store/dump.md)
- [nix-store --export](command-ref/nix-store/export.md)
- [nix-store --gc](command-ref/nix-store/gc.md)
- [nix-store --generate-binary-cache-key](command-ref/nix-store/generate-binary-cache-key.md)
- [nix-store --import](command-ref/nix-store/import.md)
- [nix-store --load-db](command-ref/nix-store/load-db.md)
- [nix-store --optimise](command-ref/nix-store/optimise.md)
- [nix-store --print-env](command-ref/nix-store/print-env.md)
- [nix-store --query](command-ref/nix-store/query.md)
- [nix-store --read-log](command-ref/nix-store/read-log.md)
- [nix-store --realise](command-ref/nix-store/realise.md)
- [nix-store --repair-path](command-ref/nix-store/repair-path.md)
- [nix-store --restore](command-ref/nix-store/restore.md)
- [nix-store --serve](command-ref/nix-store/serve.md)
- [nix-store --verify-path](command-ref/nix-store/verify-path.md)
- [nix-store --verify](command-ref/nix-store/verify.md)
- [nix-env](command-ref/nix-env.md)
- [nix-env --delete-generations](command-ref/nix-env/delete-generations.md)
- [nix-env --install](command-ref/nix-env/install.md)
- [nix-env --list-generations](command-ref/nix-env/list-generations.md)
- [nix-env --query](command-ref/nix-env/query.md)
- [nix-env --rollback](command-ref/nix-env/rollback.md)
- [nix-env --set-flag](command-ref/nix-env/set-flag.md)
- [nix-env --set](command-ref/nix-env/set.md)
- [nix-env --switch-generation](command-ref/nix-env/switch-generation.md)
- [nix-env --switch-profile](command-ref/nix-env/switch-profile.md)
- [nix-env --uninstall](command-ref/nix-env/uninstall.md)
- [nix-env --upgrade](command-ref/nix-env/upgrade.md)
- [Utilities](command-ref/utilities.md)
- [nix-channel](command-ref/nix-channel.md)
- [nix-collect-garbage](command-ref/nix-collect-garbage.md)
- [nix-copy-closure](command-ref/nix-copy-closure.md)
- [nix-daemon](command-ref/nix-daemon.md)
- [nix-hash](command-ref/nix-hash.md)
- [nix-instantiate](command-ref/nix-instantiate.md)
- [nix-prefetch-url](command-ref/nix-prefetch-url.md)
- [Experimental Commands](command-ref/experimental-commands.md)
{{#include ./command-ref/new-cli/SUMMARY.md}}
- [Files](command-ref/files.md)
- [nix.conf](command-ref/conf-file.md)
- [Profiles](command-ref/files/profiles.md)
- [manifest.nix](command-ref/files/manifest.nix.md)
- [manifest.json](command-ref/files/manifest.json.md)
- [Channels](command-ref/files/channels.md)
- [Default Nix expression](command-ref/files/default-nix-expression.md)
- [Architecture and Design](architecture/architecture.md)
- [Formats and Protocols](protocols/index.md)
- [JSON Formats](protocols/json/index.md)
- [Store Object Info](protocols/json/store-object-info.md)
- [Derivation](protocols/json/derivation.md)
- [Serving Tarball Flakes](protocols/tarball-fetcher.md)
- [Store Path Specification](protocols/store-path.md)
- [Nix Archive (NAR) Format](protocols/nix-archive.md)
- [Derivation "ATerm" file format](protocols/derivation-aterm.md)
- [C API](c-api.md)
- [Glossary](glossary.md)
- [Development](development/index.md)
- [Building](development/building.md)
- [Testing](development/testing.md)
- [Debugging](development/debugging.md)
- [Documentation](development/documentation.md)
- [CLI guideline](development/cli-guideline.md)
- [JSON guideline](development/json-guideline.md)
- [C++ style guide](development/cxx.md)
- [Experimental Features](development/experimental-features.md)
- [Contributing](development/contributing.md)
- [Determinate Nix Releases Notes](release-notes-determinate/index.md)
- [Changes between Nix and Determinate Nix](release-notes-determinate/changes.md)
- [Release 1.0 (2024-11-??)](release-notes-determinate/rl-1.0.md)
- [Nix Releases Notes](release-notes/index.md)
{{#include ./SUMMARY-rl-next.md}}
- [Release 2.26 (2025-01-22)](release-notes/rl-2.26.md)
- [Release 2.25 (2024-11-07)](release-notes/rl-2.25.md)
- [Release 2.24 (2024-07-31)](release-notes/rl-2.24.md)
- [Release 2.23 (2024-06-03)](release-notes/rl-2.23.md)
- [Release 2.22 (2024-04-23)](release-notes/rl-2.22.md)
- [Release 2.21 (2024-03-11)](release-notes/rl-2.21.md)
- [Release 2.20 (2024-01-29)](release-notes/rl-2.20.md)
- [Release 2.19 (2023-11-17)](release-notes/rl-2.19.md)
- [Release 2.18 (2023-09-20)](release-notes/rl-2.18.md)
- [Release 2.17 (2023-07-24)](release-notes/rl-2.17.md)
- [Release 2.16 (2023-05-31)](release-notes/rl-2.16.md)
- [Release 2.15 (2023-04-11)](release-notes/rl-2.15.md)
- [Release 2.14 (2023-02-28)](release-notes/rl-2.14.md)
- [Release 2.13 (2023-01-17)](release-notes/rl-2.13.md)
- [Release 2.12 (2022-12-06)](release-notes/rl-2.12.md)
- [Release 2.11 (2022-08-25)](release-notes/rl-2.11.md)
- [Release 2.10 (2022-07-11)](release-notes/rl-2.10.md)
- [Release 2.9 (2022-05-30)](release-notes/rl-2.9.md)
- [Release 2.8 (2022-04-19)](release-notes/rl-2.8.md)
- [Release 2.7 (2022-03-07)](release-notes/rl-2.7.md)
- [Release 2.6 (2022-01-24)](release-notes/rl-2.6.md)
- [Release 2.5 (2021-12-13)](release-notes/rl-2.5.md)
- [Release 2.4 (2021-11-01)](release-notes/rl-2.4.md)
- [Release 2.3 (2019-09-04)](release-notes/rl-2.3.md)
- [Release 2.2 (2019-01-11)](release-notes/rl-2.2.md)
- [Release 2.1 (2018-09-02)](release-notes/rl-2.1.md)
- [Release 2.0 (2018-02-22)](release-notes/rl-2.0.md)
- [Release 1.11.10 (2017-06-12)](release-notes/rl-1.11.10.md)
- [Release 1.11 (2016-01-19)](release-notes/rl-1.11.md)
- [Release 1.10 (2015-09-03)](release-notes/rl-1.10.md)
- [Release 1.9 (2015-06-12)](release-notes/rl-1.9.md)
- [Release 1.8 (2014-12-14)](release-notes/rl-1.8.md)
- [Release 1.7 (2014-04-11)](release-notes/rl-1.7.md)
- [Release 1.6.1 (2013-10-28)](release-notes/rl-1.6.1.md)
- [Release 1.6 (2013-09-10)](release-notes/rl-1.6.md)
- [Release 1.5.2 (2013-05-13)](release-notes/rl-1.5.2.md)
- [Release 1.5 (2013-02-27)](release-notes/rl-1.5.md)
- [Release 1.4 (2013-02-26)](release-notes/rl-1.4.md)
- [Release 1.3 (2013-01-04)](release-notes/rl-1.3.md)
- [Release 1.2 (2012-12-06)](release-notes/rl-1.2.md)
- [Release 1.1 (2012-07-18)](release-notes/rl-1.1.md)
- [Release 1.0 (2012-05-11)](release-notes/rl-1.0.md)
- [Release 0.16 (2010-08-17)](release-notes/rl-0.16.md)
- [Release 0.15 (2010-03-17)](release-notes/rl-0.15.md)
- [Release 0.14 (2010-02-04)](release-notes/rl-0.14.md)
- [Release 0.13 (2009-11-05)](release-notes/rl-0.13.md)
- [Release 0.12 (2008-11-20)](release-notes/rl-0.12.md)
- [Release 0.11 (2007-12-31)](release-notes/rl-0.11.md)
- [Release 0.10.1 (2006-10-11)](release-notes/rl-0.10.1.md)
- [Release 0.10 (2006-10-06)](release-notes/rl-0.10.md)
- [Release 0.9.2 (2005-09-21)](release-notes/rl-0.9.2.md)
- [Release 0.9.1 (2005-09-20)](release-notes/rl-0.9.1.md)
- [Release 0.9 (2005-09-16)](release-notes/rl-0.9.md)
- [Release 0.8.1 (2005-04-13)](release-notes/rl-0.8.1.md)
- [Release 0.8 (2005-04-11)](release-notes/rl-0.8.md)
- [Release 0.7 (2005-01-12)](release-notes/rl-0.7.md)
- [Release 0.6 (2004-11-14)](release-notes/rl-0.6.md)
- [Release 0.5 and earlier](release-notes/rl-0.5.md)

54
doc/manual/source/_redirects Normal file
View file

@ -0,0 +1,54 @@
# redirect rules for paths (server-side) to prevent link rot.
# see ../redirects.js for redirects based on URL fragments (client-side)
#
# concrete user story this supports:
# - user finds URL to the manual for Nix x.y
# - Nix x.z (z > y) is the most recent release
# - updating the version in the URL will show the right thing
#
# format documentation:
# - https://docs.netlify.com/routing/redirects/#syntax-for-the-redirects-file
# - https://docs.netlify.com/routing/redirects/redirect-options/
#
# conventions:
# - always force (<CODE>!) since this allows re-using file names
# - group related paths to ease readability
# - keep in alphabetical/wildcards-last order, which will reduce version control conflicts
# - redirects that should have been there but are missing can be inserted where they belong
/advanced-topics/advanced-topics /advanced-topics 301!
/command-ref/command-ref /command-ref 301!
/contributing/contributing /development 301!
/contributing /development 301!
/contributing/hacking /development/building 301!
/contributing/testing /development/testing 301!
/contributing/documentation /development/documentation 301!
/contributing/experimental-features /development/experimental-features 301!
/contributing/cli-guideline /development/cli-guideline 301!
/contributing/json-guideline /development/json-guideline 301!
/contributing/cxx /development/cxx 301!
/expressions/expression-language /language/ 301!
/expressions/language-constructs /language/constructs 301!
/expressions/language-operators /language/operators 301!
/expressions/language-values /language/values 301!
/expressions/* /language/:splat 301!
/language/values /language/types 301!
/language/constructs /language/syntax 301!
/language/builtin-constants /language/builtins 301!
/installation/installation /installation 301!
/package-management/basic-package-mgmt /command-ref/nix-env 301!
/package-management/channels /command-ref/nix-channel 301!
/package-management/package-management /package-management 301!
/package-management/s3-substituter /store/types/s3-binary-cache-store 301!
/protocols/protocols /protocols 301!
/json/* /protocols/json/:splat 301!
/release-notes/release-notes /release-notes 301!
/package-management/copy-closure /command-ref/nix-copy-closure 301!

39
doc/manual/source/advanced-topics/cores-vs-jobs.md Normal file
View file

@ -0,0 +1,39 @@
# Tuning Cores and Jobs
Nix has two relevant settings with regards to how your CPU cores will
be utilized: `cores` and `max-jobs`. This chapter will talk about what
they are, how they interact, and their configuration trade-offs.
- `max-jobs`\
Dictates how many separate derivations will be built at the same
time. If you set this to zero, the local machine will do no
builds. Nix will still substitute from binary caches, and build
remotely if remote builders are configured.
- `cores`\
Suggests how many cores each derivation should use. Similar to
`make -j`.
The `cores` setting determines the value of
`NIX_BUILD_CORES`. `NIX_BUILD_CORES` is equal to `cores`, unless
`cores` equals `0`, in which case `NIX_BUILD_CORES` will be the total
number of cores in the system.
The maximum number of consumed cores is a simple multiplication,
`max-jobs` \* `NIX_BUILD_CORES`.
The balance on how to set these two independent variables depends upon
each builder's workload and hardware. Here are a few example scenarios
on a machine with 24 cores:
| `max-jobs` | `cores` | `NIX_BUILD_CORES` | Maximum Processes | Result |
| --------------------- | ------------------ | ----------------- | ----------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| 1 | 24 | 24 | 24 | One derivation will be built at a time, each one can use 24 cores. Undersold if a job can’t use 24 cores. |
| 4 | 6 | 6 | 24 | Four derivations will be built at once, each given access to six cores. |
| 12 | 6 | 6 | 72 | 12 derivations will be built at once, each given access to six cores. This configuration is over-sold. If all 12 derivations being built simultaneously try to use all six cores, the machine's performance will be degraded due to extensive context switching between the 12 builds. |
| 24 | 1 | 1 | 24 | 24 derivations can build at the same time, each using a single core. Never oversold, but derivations which require many cores will be very slow to compile. |
| 24 | 0 | 24 | 576 | 24 derivations can build at the same time, each using all the available cores of the machine. Very likely to be oversold, and very likely to suffer context switches. |
It is up to the derivations' build script to respect host's requested
cores-per-build by following the value of the `NIX_BUILD_CORES`
environment variable.

123
doc/manual/source/advanced-topics/diff-hook.md Normal file
View file

@ -0,0 +1,123 @@
# Verifying Build Reproducibility
You can use Nix's `diff-hook` setting to compare build results. Note
that this hook is only executed if the results differ; it is not used
for determining if the results are the same.
For purposes of demonstration, we'll use the following Nix file,
`deterministic.nix` for testing:
```nix
let
inherit (import <nixpkgs> {}) runCommand;
in {
stable = runCommand "stable" {} ''
touch $out
'';
unstable = runCommand "unstable" {} ''
echo $RANDOM > $out
'';
}
```
Additionally, `nix.conf` contains:
diff-hook = /etc/nix/my-diff-hook
run-diff-hook = true
where `/etc/nix/my-diff-hook` is an executable file containing:
```bash
#!/bin/sh
exec >&2
echo "For derivation $3:"
/run/current-system/sw/bin/diff -r "$1" "$2"
```
The diff hook is executed by the same user and group who ran the build.
However, the diff hook does not have write access to the store path just
built.
# Spot-Checking Build Determinism
Verify a path which already exists in the Nix store by passing `--check`
to the build command.
If the build passes and is deterministic, Nix will exit with a status
code of 0:
```console
$ nix-build ./deterministic.nix --attr stable
this derivation will be built:
/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv
building '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
$ nix-build ./deterministic.nix --attr stable --check
checking outputs of '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
```
If the build is not deterministic, Nix will exit with a status code of
1:
```console
$ nix-build ./deterministic.nix --attr unstable
this derivation will be built:
/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv
building '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable
$ nix-build ./deterministic.nix --attr unstable --check
checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may
not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs
```
In the Nix daemon's log, we will now see:
```
For derivation /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv:
1c1
< 8108
---
> 30204
```
Using `--check` with `--keep-failed` will cause Nix to keep the second
build's output in a special, `.check` path:
```console
$ nix-build ./deterministic.nix --attr unstable --check --keep-failed
checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
note: keeping build directory '/tmp/nix-build-unstable.drv-0'
error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may
not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs
from '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check'
```
In particular, notice the
`/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check` output. Nix
has copied the build results to that directory where you can examine it.
> []{#check-dirs-are-unregistered} **Note**
>
> Check paths are not protected against garbage collection, and this
> path will be deleted on the next garbage collection.
>
> The path is guaranteed to be alive for the duration of
> the `diff-hook`'s execution, but may be deleted any time after.
>
> If the comparison is performed as part of automated tooling, please
> use the diff-hook or author your tooling to handle the case where the
> build was not deterministic and also a check path does not exist.
`--check` is only usable if the derivation has been built on the system
already. If the derivation has not been built Nix will fail with the
error:
error: some outputs of '/nix/store/hzi1h60z2qf0nb85iwnpvrai3j2w7rr6-unstable.drv'
are not valid, so checking is not possible
Run the build without `--check`, and then try with `--check` again.

108
doc/manual/source/advanced-topics/distributed-builds.md Normal file
View file

@ -0,0 +1,108 @@
# Remote Builds
A local Nix installation can forward Nix builds to other machines,
this allows multiple builds to be performed in parallel.
Remote builds also allow Nix to perform multi-platform builds in a
semi-transparent way. For example, if you perform a build for a
`x86_64-darwin` on an `i686-linux` machine, Nix can automatically
forward the build to a `x86_64-darwin` machine, if one is available.
## Requirements
For a local machine to forward a build to a remote machine, the remote machine must:
- Have Nix installed
- Be running an SSH server, e.g. `sshd`
- Be accessible via SSH from the local machine over the network
- Have the local machine's public SSH key in `/etc/ssh/authorized_keys.d/<username>`
- Have the username of the SSH user in the `trusted-users` setting in `nix.conf`
## Testing
To test connecting to a remote Nix instance (in this case `mac`), run:
```console
nix store info --store ssh://username@mac
```
To specify an SSH identity file as part of the remote store URI add a
query paramater, e.g.
```console
nix store info --store ssh://username@mac?ssh-key=/home/alice/my-key
```
Since builds should be non-interactive, the key should not have a
passphrase. Alternatively, you can load identities ahead of time into
`ssh-agent` or `gpg-agent`.
In a multi-user installation (default), builds are executed by the Nix
Daemon. The Nix Daemon cannot prompt for a passphrase via the terminal
or `ssh-agent`, so the SSH key must not have a passphrase.
In addition, the Nix Daemon's user (typically root) needs to have SSH
access to the remote builder.
Access can be verified by running `sudo su`, and then validating SSH
access, e.g. by running `ssh mac`. SSH identity files for root users
are usually stored in `/root/.ssh/` (Linux) or `/var/root/.ssh` (MacOS).
If you get the error
```console
bash: nix: command not found
error: cannot connect to 'mac'
```
then you need to ensure that the `PATH` of non-interactive login shells
contains Nix.
The [list of remote build machines](@docroot@/command-ref/conf-file.md#conf-builders) can be specified on the command line or in the Nix configuration file.
For example, the following command allows you to build a derivation for `x86_64-darwin` on a Linux machine:
```console
uname
```
```console
Linux
```
```console
nix build --impure \
--expr '(with import <nixpkgs> { system = "x86_64-darwin"; }; runCommand "foo" {} "uname > $out")' \
--builders 'ssh://mac x86_64-darwin'
```
```console
[1/0/1 built, 0.0 MiB DL] building foo on ssh://mac
```
```console
cat ./result
```
```console
Darwin
```
It is possible to specify multiple build machines separated by a semicolon or a newline, e.g.
```console
--builders 'ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd'
```
Remote build machines can also be configured in [`nix.conf`](@docroot@/command-ref/conf-file.md), e.g.
builders = ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd
After making changes to `nix.conf`, restart the Nix daemon for changes to take effect.
Finally, remote build machines can be configured in a separate configuration
file included in `builders` via the syntax `@/path/to/file`. For example,
builders = @/etc/nix/machines
causes the list of machines in `/etc/nix/machines` to be included.
(This is the default.)

1
doc/manual/source/advanced-topics/index.md Normal file
View file

@ -0,0 +1 @@
This section lists advanced topics related to builds and builds performance

127
doc/manual/source/advanced-topics/post-build-hook.md Normal file
View file

@ -0,0 +1,127 @@
# Using the `post-build-hook`
# Implementation Caveats
Here we use the post-build hook to upload to a binary cache. This is a
simple and working example, but it is not suitable for all use cases.
The post build hook program runs after each executed build, and blocks
the build loop. The build loop exits if the hook program fails.
Concretely, this implementation will make Nix slow or unusable when the
internet is slow or unreliable.
A more advanced implementation might pass the store paths to a
user-supplied daemon or queue for processing the store paths outside of
the build loop.
# Prerequisites
This tutorial assumes you have configured an [S3-compatible binary cache](@docroot@/command-ref/new-cli/nix3-help-stores.md#s3-binary-cache-store) as a [substituter](../command-ref/conf-file.md#conf-substituters),
and that the `root` user's default AWS profile can upload to the bucket.
# Set up a Signing Key
Use `nix-store --generate-binary-cache-key` to create our public and
private signing keys. We will sign paths with the private key, and
distribute the public key for verifying the authenticity of the paths.
```console
# nix-store --generate-binary-cache-key example-nix-cache-1 /etc/nix/key.private /etc/nix/key.public
# cat /etc/nix/key.public
example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
```
Then update [`nix.conf`](../command-ref/conf-file.md) on any machine that will access the cache.
Add the cache URL to [`substituters`](../command-ref/conf-file.md#conf-substituters) and the public key to [`trusted-public-keys`](../command-ref/conf-file.md#conf-trusted-public-keys):
substituters = https://cache.nixos.org/ s3://example-nix-cache
trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
Machines that build for the cache must sign derivations using the private key.
On those machines, add the path to the key file to the [`secret-key-files`](../command-ref/conf-file.md#conf-secret-key-files) field in their [`nix.conf`](../command-ref/conf-file.md):
secret-key-files = /etc/nix/key.private
We will restart the Nix daemon in a later step.
# Implementing the build hook
Write the following script to `/etc/nix/upload-to-cache.sh`:
```bash
#!/bin/sh
set -eu
set -f # disable globbing
export IFS=' '
echo "Uploading paths" $OUT_PATHS
exec nix copy --to "s3://example-nix-cache" $OUT_PATHS
```
> **Note**
>
> The `$OUT_PATHS` variable is a space-separated list of Nix store
> paths. In this case, we expect and want the shell to perform word
> splitting to make each output path its own argument to `nix
> store sign`. Nix guarantees the paths will not contain any spaces,
> however a store path might contain glob characters. The `set -f`
> disables globbing in the shell.
> If you want to upload the `.drv` file too, the `$DRV_PATH` variable
> is also defined for the script and works just like `$OUT_PATHS`.
Then make sure the hook program is executable by the `root` user:
```console
# chmod +x /etc/nix/upload-to-cache.sh
```
# Updating Nix Configuration
Edit `/etc/nix/nix.conf` to run our hook, by adding the following
configuration snippet at the end:
post-build-hook = /etc/nix/upload-to-cache.sh
Then, restart the `nix-daemon`.
# Testing
Build any derivation, for example:
```console
$ nix-build --expr '(import <nixpkgs> {}).writeText "example" (builtins.toString builtins.currentTime)'
this derivation will be built:
/nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv
building '/nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv'...
running post-build-hook '/home/grahamc/projects/github.com/NixOS/nix/post-hook.sh'...
post-build-hook: Signing paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
post-build-hook: Uploading paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
/nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
```
Then delete the path from the store, and try substituting it from the
binary cache:
```console
$ rm ./result
$ nix-store --delete /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
```
Now, copy the path back from the cache:
```console
$ nix-store --realise /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
copying path '/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example from 's3://example-nix-cache'...
warning: you did not specify '--add-root'; the result might be removed by the garbage collector
/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example
```
# Conclusion
We now have a Nix installation configured to automatically sign and
upload every local build to a remote binary cache.
Before deploying this to production, be sure to consider the
[implementation caveats](#implementation-caveats).

116
doc/manual/source/architecture/architecture.md Normal file
View file

@ -0,0 +1,116 @@
# Architecture
This chapter describes how Nix works.
It should help users understand why Nix behaves as it does, and it should help developers understand how to modify Nix and how to write similar tools.
## Overview
Nix consists of [hierarchical layers].
[hierarchical layers]: https://en.wikipedia.org/wiki/Multitier_architecture#Layers
The following [concept map] shows its main components (rectangles), the objects they operate on (rounded rectangles), and their interactions (connecting phrases):
[concept map]: https://en.wikipedia.org/wiki/Concept_map
```
.----------------.
| Nix expression |----------.
'----------------' |
| passed to
| |
+----------|-------------------|--------------------------------+
| Nix | V |
| | +-------------------------+ |
| | | commmand line interface |------. |
| | +-------------------------+ | |
| | | | |
| evaluated by calls manages |
| | | | |
| | V | |
| | +--------------------+ | |
| '-------->| language evaluator | | |
| +--------------------+ | |
| | | |
| produces | |
| | V |
| +----------------------------|------------------------------+ |
| | store | | |
| | referenced by V builds | |
| | .-------------. .------------. .--------------. | |
| | | build input |----->| build plan |----->| build result | | |
| | '-------------' '------------' '--------------' | |
| +-------------------------------------------------|---------+ |
+---------------------------------------------------|-----------+
|
represented as
|
V
.---------------.
| file |
'---------------'
```
At the top is the [command line interface](../command-ref/index.md) that drives the underlying layers.
The [Nix language](../language/index.md) evaluator transforms Nix expressions into self-contained *build plans*, which are used to derive *build results* from referenced *build inputs*.
The command line interface and Nix expressions are what users deal with most.
> **Note**
>
> The Nix language itself does not have a notion of *packages* or *configurations*.
> As far as we are concerned here, the inputs and results of a build plan are just data.
Underlying the command line interface and the Nix language evaluator is the [Nix store](../store/index.md), a mechanism to keep track of build plans, data, and references between them.
It can also execute build plans to produce new data, which are made available to the operating system as files.
A build plan itself is a series of *build tasks*, together with their build inputs.
> **Important**
> A build task in Nix is called [derivation](@docroot@/glossary.md#gloss-derivation).
Each build task has a special build input executed as *build instructions* in order to perform the build.
The result of a build task can be input to another build task.
The following [data flow diagram] shows a build plan for illustration.
Build inputs used as instructions to a build task are marked accordingly:
[data flow diagram]: https://en.wikipedia.org/wiki/Data-flow_diagram
```
+--------------------------------------------------------------------+
| build plan |
| |
| .-------------. |
| | build input |---------. |
| '-------------' | |
| instructions |
| | |
| v |
| .-------------. .----------. |
| | build input |-->( build task )-------. |
| '-------------' '----------' | |
| instructions |
| | |
| v |
| .-------------. .----------. .--------------. |
| | build input |---------. ( build task )--->| build result | |
| '-------------' | '----------' '--------------' |
| instructions ^ |
| | | |
| v | |
| .-------------. .----------. | |
| | build input |-->( build task )-------' |
| '-------------' '----------' |
| ^ |
| | |
| | |
| .-------------. | |
| | build input |---------' |
| '-------------' |
| |
+--------------------------------------------------------------------+
```

16
doc/manual/source/c-api.md Normal file
View file

@ -0,0 +1,16 @@
# C API
Nix provides a C API with the intent of [_becoming_](https://github.com/NixOS/nix/milestone/52) a stable API, which it is currently not.
It is in development.
See:
- C API documentation for a recent build of master
- [Getting Started]
- [Index]
- [Matrix Room *Nix Bindings*](https://matrix.to/#/#nix-bindings:nixos.org) for discussion and questions.
- [Stabilisation Milestone](https://github.com/NixOS/nix/milestone/52)
- [Other C API PRs and issues](https://github.com/NixOS/nix/labels/c%20api)
- [Contributing C API Documentation](development/documentation.md#c-api-documentation), including how to build it locally.
[Getting Started]: https://hydra.nixos.org/job/nix/master/external-api-docs/latest/download-by-type/doc/external-api-docs
[Index]: https://hydra.nixos.org/job/nix/master/external-api-docs/latest/download-by-type/doc/external-api-docs/globals.html

77
doc/manual/source/command-ref/conf-file-prefix.md Normal file
View file

@ -0,0 +1,77 @@
# Name
`nix.conf` - Nix configuration file
# Description
Nix supports a variety of configuration settings, which are read from configuration files or taken as command line flags.
## Configuration file
By default Nix reads settings from the following places, in that order:
1. The system-wide configuration file `sysconfdir/nix/nix.conf` (i.e. `/etc/nix/nix.conf` on most systems), or `$NIX_CONF_DIR/nix.conf` if [`NIX_CONF_DIR`](./env-common.md#env-NIX_CONF_DIR) is set.
Values loaded in this file are not forwarded to the Nix daemon.
The client assumes that the daemon has already loaded them.
1. If [`NIX_USER_CONF_FILES`](./env-common.md#env-NIX_USER_CONF_FILES) is set, then each path separated by `:` will be loaded in reverse order.
Otherwise it will look for `nix/nix.conf` files in `XDG_CONFIG_DIRS` and [`XDG_CONFIG_HOME`](./env-common.md#env-XDG_CONFIG_HOME).
If unset, `XDG_CONFIG_DIRS` defaults to `/etc/xdg`, and `XDG_CONFIG_HOME` defaults to `$HOME/.config` as per [XDG Base Directory Specification](https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html).
1. If [`NIX_CONFIG`](./env-common.md#env-NIX_CONFIG) is set, its contents are treated as the contents of a configuration file.
### File format
Configuration files consist of `name = value` pairs, one per line.
Comments start with a `#` character.
Example:
```
keep-outputs = true # Nice for developers
keep-derivations = true # Idem
```
Other files can be included with a line like `include <path>`, where `<path>` is interpreted relative to the current configuration file.
A missing file is an error unless `!include` is used instead.
A configuration setting usually overrides any previous value.
However, for settings that take a list of items, you can prefix the name of the setting by `extra-` to *append* to the previous value.
For instance,
```
substituters = a b
extra-substituters = c d
```
defines the `substituters` setting to be `a b c d`.
Unknown option names are not an error, and are simply ignored with a warning.
## Command line flags
Configuration options can be set on the command line, overriding the values set in the [configuration file](#configuration-file):
- Every configuration setting has corresponding command line flag (e.g. `--max-jobs 16`).
Boolean settings do not need an argument, and can be explicitly disabled with the `no-` prefix (e.g. `--keep-failed` and `--no-keep-failed`).
Unknown option names are invalid flags (unless there is already a flag with that name), and are rejected with an error.
- The flag `--option <name> <value>` is interpreted exactly like a `<name> = <value>` in a setting file.
Unknown option names are ignored with a warning.
The `extra-` prefix is supported for settings that take a list of items (e.g. `--extra-trusted users alice` or `--option extra-trusted-users alice`).
## Integer settings
Settings that have an integer type support the suffixes `K`, `M`, `G`
and `T`. These cause the specified value to be multiplied by 2^10,
2^20, 2^30 and 2^40, respectively. For instance, `--min-free 1M` is
equivalent to `--min-free 1048576`.
# Available settings

156
doc/manual/source/command-ref/env-common.md Normal file
View file

@ -0,0 +1,156 @@
# Common Environment Variables
Most Nix commands interpret the following environment variables:
- <span id="env-IN_NIX_SHELL">[`IN_NIX_SHELL`](#env-IN_NIX_SHELL)</span>
Indicator that tells if the current environment was set up by
`nix-shell`. It can have the values `pure` or `impure`.
- <span id="env-NIX_PATH">[`NIX_PATH`](#env-NIX_PATH)</span>
A colon-separated list of search path entries used to resolve [lookup paths](@docroot@/language/constructs/lookup-path.md).
This environment variable overrides the value of the [`nix-path` configuration setting](@docroot@/command-ref/conf-file.md#conf-nix-path).
It can be extended using the [`-I` option](@docroot@/command-ref/opt-common.md#opt-I).
> **Example**
>
> ```bash
> $ export NIX_PATH=`/home/eelco/Dev:nixos-config=/etc/nixos
> ```
If `NIX_PATH` is set to an empty string, resolving search paths will always fail.
> **Example**
>
> ```bash
> $ NIX_PATH= nix-instantiate --eval '<nixpkgs>'
> error: file 'nixpkgs' was not found in the Nix search path (add it using $NIX_PATH or -I)
> ```
- <span id="env-NIX_IGNORE_SYMLINK_STORE">[`NIX_IGNORE_SYMLINK_STORE`](#env-NIX_IGNORE_SYMLINK_STORE)</span>
Normally, the Nix store directory (typically `/nix/store`) is not
allowed to contain any symlink components. This is to prevent
“impure” builds. Builders sometimes “canonicalise” paths by
resolving all symlink components. Thus, builds on different machines
(with `/nix/store` resolving to different locations) could yield
different results. This is generally not a problem, except when
builds are deployed to machines where `/nix/store` resolves
differently. If you are sure that you’re not going to do that, you
can set `NIX_IGNORE_SYMLINK_STORE` to `1`.
Note that if you’re symlinking the Nix store so that you can put it
on another file system than the root file system, on Linux you’re
better off using `bind` mount points, e.g.,
```console
$ mkdir /nix
$ mount -o bind /mnt/otherdisk/nix /nix
```
Consult the mount 8 manual page for details.
- <span id="env-NIX_STORE_DIR">[`NIX_STORE_DIR`](#env-NIX_STORE_DIR)</span>
Overrides the location of the Nix store (default `prefix/store`).
- <span id="env-NIX_DATA_DIR">[`NIX_DATA_DIR`](#env-NIX_DATA_DIR)</span>
Overrides the location of the Nix static data directory (default
`prefix/share`).
- <span id="env-NIX_LOG_DIR">[`NIX_LOG_DIR`](#env-NIX_LOG_DIR)</span>
Overrides the location of the Nix log directory (default
`prefix/var/log/nix`).
- <span id="env-NIX_STATE_DIR">[`NIX_STATE_DIR`](#env-NIX_STATE_DIR)</span>
Overrides the location of the Nix state directory (default
`prefix/var/nix`).
- <span id="env-NIX_CONF_DIR">[`NIX_CONF_DIR`](#env-NIX_CONF_DIR)</span>
Overrides the location of the system Nix configuration directory
(default `prefix/etc/nix`).
- <span id="env-NIX_CONFIG">[`NIX_CONFIG`](#env-NIX_CONFIG)</span>
Applies settings from Nix configuration from the environment.
The content is treated as if it was read from a Nix configuration file.
Settings are separated by the newline character.
- <span id="env-NIX_USER_CONF_FILES">[`NIX_USER_CONF_FILES`](#env-NIX_USER_CONF_FILES)</span>
Overrides the location of the Nix user configuration files to load from.
The default are the locations according to the [XDG Base Directory Specification].
See the [XDG Base Directories](#xdg-base-directories) sub-section for details.
The variable is treated as a list separated by the `:` token.
- <span id="env-TMPDIR">[`TMPDIR`](#env-TMPDIR)</span>
Use the specified directory to store temporary files. In particular,
this includes temporary build directories; these can take up
substantial amounts of disk space. The default is `/tmp`.
- <span id="env-NIX_REMOTE">[`NIX_REMOTE`](#env-NIX_REMOTE)</span>
This variable should be set to `daemon` if you want to use the Nix
daemon to execute Nix operations. This is necessary in [multi-user
Nix installations](@docroot@/installation/multi-user.md). If the Nix
daemon's Unix socket is at some non-standard path, this variable
should be set to `unix://path/to/socket`. Otherwise, it should be
left unset.
- <span id="env-NIX_SHOW_STATS">[`NIX_SHOW_STATS`](#env-NIX_SHOW_STATS)</span>
If set to `1`, Nix will print some evaluation statistics, such as
the number of values allocated.
- <span id="env-NIX_COUNT_CALLS">[`NIX_COUNT_CALLS`](#env-NIX_COUNT_CALLS)</span>
If set to `1`, Nix will print how often functions were called during
Nix expression evaluation. This is useful for profiling your Nix
expressions.
- <span id="env-GC_INITIAL_HEAP_SIZE">[`GC_INITIAL_HEAP_SIZE`](#env-GC_INITIAL_HEAP_SIZE)</span>
If Nix has been configured to use the Boehm garbage collector, this
variable sets the initial size of the heap in bytes. It defaults to
384 MiB. Setting it to a low value reduces memory consumption, but
will increase runtime due to the overhead of garbage collection.
## XDG Base Directories
Nix follows the [XDG Base Directory Specification].
For backwards compatibility, Nix commands will follow the standard only when [`use-xdg-base-directories`] is enabled.
[New Nix commands](@docroot@/command-ref/new-cli/nix.md) (experimental) conform to the standard by default.
The following environment variables are used to determine locations of various state and configuration files:
- [`XDG_CONFIG_HOME`]{#env-XDG_CONFIG_HOME} (default `~/.config`)
- [`XDG_STATE_HOME`]{#env-XDG_STATE_HOME} (default `~/.local/state`)
- [`XDG_CACHE_HOME`]{#env-XDG_CACHE_HOME} (default `~/.cache`)
[XDG Base Directory Specification]: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
[`use-xdg-base-directories`]: @docroot@/command-ref/conf-file.md#conf-use-xdg-base-directories
In addition, setting the following environment variables overrides the XDG base directories:
- [`NIX_CONFIG_HOME`]{#env-NIX_CONFIG_HOME} (default `$XDG_CONFIG_HOME/nix`)
- [`NIX_STATE_HOME`]{#env-NIX_STATE_HOME} (default `$XDG_STATE_HOME/nix`)
- [`NIX_CACHE_HOME`]{#env-NIX_CACHE_HOME} (default `$XDG_CACHE_HOME/nix`)
When [`use-xdg-base-directories`] is enabled, the configuration directory is:
1. `$NIX_CONFIG_HOME`, if it is defined
2. Otherwise, `$XDG_CONFIG_HOME/nix`, if `XDG_CONFIG_HOME` is defined
3. Otherwise, `~/.config/nix`.
Likewise for the state and cache directories.

8
doc/manual/source/command-ref/experimental-commands.md Normal file
View file

@ -0,0 +1,8 @@
# Experimental Commands
This section lists [experimental commands](@docroot@/development/experimental-features.md#xp-feature-nix-command).
> **Warning**
>
> These commands may be removed in the future, or their syntax may
> change in incompatible ways.

4
doc/manual/source/command-ref/files.md Normal file
View file

@ -0,0 +1,4 @@
# Files
This section lists configuration files that you can use when you work
with Nix.

26
doc/manual/source/command-ref/files/channels.md Normal file
View file

@ -0,0 +1,26 @@
## Channels
A directory containing symlinks to Nix channels, managed by [`nix-channel`]:
- `$XDG_STATE_HOME/nix/profiles/channels` for regular users
- `$NIX_STATE_DIR/profiles/per-user/root/channels` for `root`
[`nix-channel`] uses a [profile](@docroot@/command-ref/files/profiles.md) to store channels.
This profile contains symlinks to the contents of those channels.
## Subscribed channels
The list of subscribed channels is stored in
- `~/.nix-channels`
- `$XDG_STATE_HOME/nix/channels` if [`use-xdg-base-directories`] is set to `true`
in the following format:
```
<url> <name>
...
```
[`nix-channel`]: @docroot@/command-ref/nix-channel.md
[`use-xdg-base-directories`]: @docroot@/command-ref/conf-file.md#conf-use-xdg-base-directories

54
doc/manual/source/command-ref/files/default-nix-expression.md Normal file
View file

@ -0,0 +1,54 @@
## Default Nix expression
The source for the [Nix expressions](@docroot@/glossary.md#gloss-nix-expression) used by [`nix-env`] by default:
- `~/.nix-defexpr`
- `$XDG_STATE_HOME/nix/defexpr` if [`use-xdg-base-directories`] is set to `true`.
It is loaded as follows:
- If the default expression is a file, it is loaded as a Nix expression.
- If the default expression is a directory containing a `default.nix` file, that `default.nix` file is loaded as a Nix expression.
- If the default expression is a directory without a `default.nix` file, then its contents (both files and subdirectories) are loaded as Nix expressions.
The expressions are combined into a single attribute set, each expression under an attribute with the same name as the original file or subdirectory.
Subdirectories without a `default.nix` file are traversed recursively in search of more Nix expressions, but the names of these intermediate directories are not added to the attribute paths of the default Nix expression.
Then, the resulting expression is interpreted like this:
- If the expression is an attribute set, it is used as the default Nix expression.
- If the expression is a function, an empty set is passed as argument and the return value is used as the default Nix expression.
> **Example**
>
> If the default expression contains two files, `foo.nix` and `bar.nix`, then the default Nix expression will be equivalent to
>
> ```nix
> {
> foo = import ~/.nix-defexpr/foo.nix;
> bar = import ~/.nix-defexpr/bar.nix;
> }
> ```
The file [`manifest.nix`](@docroot@/command-ref/files/manifest.nix.md) is always ignored.
The command [`nix-channel`] places a symlink to the current user's [channels] in this directory, the [user channel link](#user-channel-link).
This makes all subscribed channels available as attributes in the default expression.
## User channel link
A symlink that ensures that [`nix-env`] can find the current user's [channels]:
- `~/.nix-defexpr/channels`
- `$XDG_STATE_HOME/defexpr/channels` if [`use-xdg-base-directories`] is set to `true`.
This symlink points to:
- `$XDG_STATE_HOME/profiles/channels` for regular users
- `$NIX_STATE_DIR/profiles/per-user/root/channels` for `root`
In a multi-user installation, you may also have `~/.nix-defexpr/channels_root`, which links to the channels of the root user.
[`nix-channel`]: @docroot@/command-ref/nix-channel.md
[`nix-env`]: @docroot@/command-ref/nix-env.md
[`use-xdg-base-directories`]: @docroot@/command-ref/conf-file.md#conf-use-xdg-base-directories
[channels]: @docroot@/command-ref/files/channels.md

45
doc/manual/source/command-ref/files/manifest.json.md Normal file
View file

@ -0,0 +1,45 @@
## `manifest.json`
The manifest file records the provenance of the packages that are installed in a [profile](./profiles.md) managed by [`nix profile`](@docroot@/command-ref/new-cli/nix3-profile.md) (experimental).
Here is an example of what the file might look like after installing `zoom-us` from Nixpkgs:
```json
{
"version": 1,
"elements": [
{
"active": true,
"attrPath": "legacyPackages.x86_64-linux.zoom-us",
"originalUrl": "flake:nixpkgs",
"storePaths": [
"/nix/store/wbhg2ga8f3h87s9h5k0slxk0m81m4cxl-zoom-us-5.3.469451.0927"
],
"uri": "github:NixOS/nixpkgs/13d0c311e3ae923a00f734b43fd1d35b47d8943a"
},
…
]
}
```
Each object in the array `elements` denotes an installed package and
has the following fields:
* `originalUrl`: The [flake reference](@docroot@/command-ref/new-cli/nix3-flake.md) specified by
the user at the time of installation (e.g. `nixpkgs`). This is also
the flake reference that will be used by `nix profile upgrade`.
* `uri`: The locked flake reference to which `originalUrl` resolved.
* `attrPath`: The flake output attribute that provided this
package. Note that this is not necessarily the attribute that the
user specified, but the one resulting from applying the default
attribute paths and prefixes; for instance, `hello` might resolve to
`packages.x86_64-linux.hello` and the empty string to
`packages.x86_64-linux.default`.
* `storePath`: The paths in the Nix store containing the package.
* `active`: Whether the profile contains symlinks to the files of this
package. If set to false, the package is kept in the Nix store, but
is not "visible" in the profile's symlink tree.

128
doc/manual/source/command-ref/files/manifest.nix.md Normal file
View file

@ -0,0 +1,128 @@
## `manifest.nix`
The manifest file records the provenance of the packages that are installed in a [profile](./profiles.md) managed by [`nix-env`](@docroot@/command-ref/nix-env.md).
Here is an example of how this file might look like after installing `hello` from Nixpkgs:
```nix
[{
meta = {
available = true;
broken = false;
changelog =
"https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v2.12.1";
description = "A program that produces a familiar, friendly greeting";
homepage = "https://www.gnu.org/software/hello/manual/";
insecure = false;
license = {
deprecated = false;
free = true;
fullName = "GNU General Public License v3.0 or later";
redistributable = true;
shortName = "gpl3Plus";
spdxId = "GPL-3.0-or-later";
url = "https://spdx.org/licenses/GPL-3.0-or-later.html";
};
longDescription = ''
GNU Hello is a program that prints "Hello, world!" when you run it.
It is fully customizable.
'';
maintainers = [{
email = "edolstra+nixpkgs@gmail.com";
github = "edolstra";
githubId = 1148549;
name = "Eelco Dolstra";
}];
name = "hello-2.12.1";
outputsToInstall = [ "out" ];
platforms = [
"i686-cygwin"
"x86_64-cygwin"
"x86_64-darwin"
"i686-darwin"
"aarch64-darwin"
"armv7a-darwin"
"i686-freebsd13"
"x86_64-freebsd13"
"aarch64-genode"
"i686-genode"
"x86_64-genode"
"x86_64-solaris"
"js-ghcjs"
"aarch64-linux"
"armv5tel-linux"
"armv6l-linux"
"armv7a-linux"
"armv7l-linux"
"i686-linux"
"m68k-linux"
"microblaze-linux"
"microblazeel-linux"
"mipsel-linux"
"mips64el-linux"
"powerpc64-linux"
"powerpc64le-linux"
"riscv32-linux"
"riscv64-linux"
"s390-linux"
"s390x-linux"
"x86_64-linux"
"mmix-mmixware"
"aarch64-netbsd"
"armv6l-netbsd"
"armv7a-netbsd"
"armv7l-netbsd"
"i686-netbsd"
"m68k-netbsd"
"mipsel-netbsd"
"powerpc-netbsd"
"riscv32-netbsd"
"riscv64-netbsd"
"x86_64-netbsd"
"aarch64_be-none"
"aarch64-none"
"arm-none"
"armv6l-none"
"avr-none"
"i686-none"
"microblaze-none"
"microblazeel-none"
"msp430-none"
"or1k-none"
"m68k-none"
"powerpc-none"
"powerpcle-none"
"riscv32-none"
"riscv64-none"
"rx-none"
"s390-none"
"s390x-none"
"vc4-none"
"x86_64-none"
"i686-openbsd"
"x86_64-openbsd"
"x86_64-redox"
"wasm64-wasi"
"wasm32-wasi"
"x86_64-windows"
"i686-windows"
];
position =
"/nix/store/7niq32w715567hbph0q13m5lqna64c1s-nixos-unstable.tar.gz/nixos-unstable.tar.gz/pkgs/applications/misc/hello/default.nix:34";
unfree = false;
unsupported = false;
};
name = "hello-2.12.1";
out = {
outPath = "/nix/store/260q5867crm1xjs4khgqpl6vr9kywql1-hello-2.12.1";
};
outPath = "/nix/store/260q5867crm1xjs4khgqpl6vr9kywql1-hello-2.12.1";
outputs = [ "out" ];
system = "x86_64-linux";
type = "derivation";
}]
```
Each element in this list corresponds to an installed package.
It incorporates some attributes of the original derivation, including `meta`, `name`, `out`, `outPath`, `outputs`, `system`.
This information is used by Nix for querying and updating the package.

74
doc/manual/source/command-ref/files/profiles.md Normal file
View file

@ -0,0 +1,74 @@
## Profiles
A directory that contains links to profiles managed by [`nix-env`] and [`nix profile`]:
- `$XDG_STATE_HOME/nix/profiles` for regular users
- `$NIX_STATE_DIR/profiles/per-user/root` if the user is `root`
A profile is a directory of symlinks to files in the Nix store.
### Filesystem layout
Profiles are versioned as follows. When using a profile named *path*, *path* is a symlink to *path*`-`*N*`-link`, where *N* is the version of the profile.
In turn, *path*`-`*N*`-link` is a symlink to a path in the Nix store.
For example:
```console
$ ls -l ~alice/.local/state/nix/profiles/profile*
lrwxrwxrwx 1 alice users 14 Nov 25 14:35 /home/alice/.local/state/nix/profiles/profile -> profile-7-link
lrwxrwxrwx 1 alice users 51 Oct 28 16:18 /home/alice/.local/state/nix/profiles/profile-5-link -> /nix/store/q69xad13ghpf7ir87h0b2gd28lafjj1j-profile
lrwxrwxrwx 1 alice users 51 Oct 29 13:20 /home/alice/.local/state/nix/profiles/profile-6-link -> /nix/store/6bvhpysd7vwz7k3b0pndn7ifi5xr32dg-profile
lrwxrwxrwx 1 alice users 51 Nov 25 14:35 /home/alice/.local/state/nix/profiles/profile-7-link -> /nix/store/mp0x6xnsg0b8qhswy6riqvimai4gm677-profile
```
Each of these symlinks is a root for the Nix garbage collector.
The contents of the store path corresponding to each version of the
profile is a tree of symlinks to the files of the installed packages,
e.g.
```console
$ ll -R ~eelco/.local/state/nix/profiles/profile-7-link/
/home/eelco/.local/state/nix/profiles/profile-7-link/:
total 20
dr-xr-xr-x 2 root root 4096 Jan 1 1970 bin
-r--r--r-- 2 root root 1402 Jan 1 1970 manifest.nix
dr-xr-xr-x 4 root root 4096 Jan 1 1970 share
/home/eelco/.local/state/nix/profiles/profile-7-link/bin:
total 20
lrwxrwxrwx 5 root root 79 Jan 1 1970 chromium -> /nix/store/ijm5k0zqisvkdwjkc77mb9qzb35xfi4m-chromium-86.0.4240.111/bin/chromium
lrwxrwxrwx 7 root root 87 Jan 1 1970 spotify -> /nix/store/w9182874m1bl56smps3m5zjj36jhp3rn-spotify-1.1.26.501.gbe11e53b-15/bin/spotify
lrwxrwxrwx 3 root root 79 Jan 1 1970 zoom-us -> /nix/store/wbhg2ga8f3h87s9h5k0slxk0m81m4cxl-zoom-us-5.3.469451.0927/bin/zoom-us
/home/eelco/.local/state/nix/profiles/profile-7-link/share/applications:
total 12
lrwxrwxrwx 4 root root 120 Jan 1 1970 chromium-browser.desktop -> /nix/store/4cf803y4vzfm3gyk3vzhzb2327v0kl8a-chromium-unwrapped-86.0.4240.111/share/applications/chromium-browser.desktop
lrwxrwxrwx 7 root root 110 Jan 1 1970 spotify.desktop -> /nix/store/w9182874m1bl56smps3m5zjj36jhp3rn-spotify-1.1.26.501.gbe11e53b-15/share/applications/spotify.desktop
lrwxrwxrwx 3 root root 107 Jan 1 1970 us.zoom.Zoom.desktop -> /nix/store/wbhg2ga8f3h87s9h5k0slxk0m81m4cxl-zoom-us-5.3.469451.0927/share/applications/us.zoom.Zoom.desktop
…
```
Each profile version contains a manifest file:
- [`manifest.nix`](@docroot@/command-ref/files/manifest.nix.md) used by [`nix-env`](@docroot@/command-ref/nix-env.md).
- [`manifest.json`](@docroot@/command-ref/files/manifest.json.md) used by [`nix profile`](@docroot@/command-ref/new-cli/nix3-profile.md) (experimental).
## User profile link
A symbolic link to the user's current profile:
- `~/.nix-profile`
- `$XDG_STATE_HOME/nix/profile` if [`use-xdg-base-directories`] is set to `true`.
By default, this symlink points to:
- `$XDG_STATE_HOME/nix/profiles/profile` for regular users
- `$NIX_STATE_DIR/profiles/per-user/root/profile` for `root`
The `PATH` environment variable should include `/bin` subdirectory of the profile link (e.g. `~/.nix-profile/bin`) for the user environment to be visible to the user.
The [installer](@docroot@/installation/installing-binary.md) sets this up by default, unless you enable [`use-xdg-base-directories`].
[`nix-env`]: @docroot@/command-ref/nix-env.md
[`nix profile`]: @docroot@/command-ref/new-cli/nix3-profile.md
[`use-xdg-base-directories`]: @docroot@/command-ref/conf-file.md#conf-use-xdg-base-directories

2
doc/manual/source/command-ref/index.md Normal file
View file

@ -0,0 +1,2 @@
This section lists commands and options that you can use when you work
with Nix.

4
doc/manual/source/command-ref/main-commands.md Normal file
View file

@ -0,0 +1,4 @@
# Main Commands
This section lists commands and options that you can use when you work
with Nix.

63
doc/manual/source/command-ref/meson.build Normal file
View file

@ -0,0 +1,63 @@
xp_features_json = custom_target(
command : [nix, '__dump-xp-features'],
capture : true,
output : 'xp-features.json',
)
experimental_features_shortlist_md = custom_target(
command : nix_eval_for_docs + [
'--expr',
'import @INPUT0@ (builtins.fromJSON (builtins.readFile ./@INPUT1@))',
],
input : [
'../../generate-xp-features-shortlist.nix',
xp_features_json,
],
output : 'experimental-features-shortlist.md',
capture : true,
env : nix_env_for_docs,
)
nix3_cli_files = custom_target(
command : [
python.full_path(),
'@INPUT0@',
'@OUTPUT@',
'--'
] + nix_eval_for_docs + [
'--expr',
'import @INPUT1@ true (builtins.readFile ./@INPUT2@)',
],
input : [
'../../remove_before_wrapper.py',
'../../generate-manpage.nix',
nix3_cli_json,
],
output : 'new-cli',
env : nix_env_for_docs,
)
conf_file_md_body = custom_target(
command : [
nix_eval_for_docs,
'--expr',
'import @INPUT0@ { prefix = "conf"; } (builtins.fromJSON (builtins.readFile ./@INPUT1@))',
],
capture : true,
input : [
'../../generate-settings.nix',
conf_file_json,
],
output : 'conf-file.body.md',
env : nix_env_for_docs,
)
conf_file_md = custom_target(
command : [ 'cat', '@INPUT0@', '@INPUT1@' ],
capture : true,
input : [
'conf-file-prefix.md',
conf_file_md_body,
],
output : 'conf-file.md',
)

125
doc/manual/source/command-ref/nix-build.md Normal file
View file

@ -0,0 +1,125 @@
# Name
`nix-build` - build a Nix expression
# Synopsis
`nix-build` [*paths…*]
[`--arg` *name* *value*]
[`--argstr` *name* *value*]
[{`--attr` | `-A`} *attrPath*]
[`--no-out-link`]
[`--dry-run`]
[{`--out-link` | `-o`} *outlink*]
# Disambiguation
This man page describes the command `nix-build`, which is distinct from `nix
build`. For documentation on the latter, run `nix build --help` or see `man
nix3-build`.
# Description
The `nix-build` command builds the derivations described by the Nix
expressions in *paths*. If the build succeeds, it places a symlink to
the result in the current directory. The symlink is called `result`. If
there are multiple Nix expressions, or the Nix expressions evaluate to
multiple derivations, multiple sequentially numbered symlinks are
created (`result`, `result-2`, and so on).
If no *paths* are specified, then `nix-build` will use `default.nix` in
the current directory, if it exists.
If an element of *paths* starts with `http://` or `https://`, it is
interpreted as the URL of a tarball that will be downloaded and unpacked
to a temporary location. The tarball must include a single top-level
directory containing at least a file named `default.nix`.
`nix-build` is essentially a wrapper around
[`nix-instantiate`](nix-instantiate.md) (to translate a high-level Nix
expression to a low-level [store derivation]) and [`nix-store
--realise`](@docroot@/command-ref/nix-store/realise.md) (to build the store
derivation).
[store derivation]: @docroot@/glossary.md#gloss-store-derivation
> **Warning**
>
> The result of the build is automatically registered as a root of the
> Nix garbage collector. This root disappears automatically when the
> `result` symlink is deleted or renamed. So don’t rename the symlink.
# Options
All options not listed here are passed to
[`nix-store --realise`](nix-store/realise.md),
except for `--arg` and `--attr` / `-A` which are passed to [`nix-instantiate`](nix-instantiate.md).
- <span id="opt-no-out-link">[`--no-out-link`](#opt-no-out-link)<span>
Do not create a symlink to the output path. Note that as a result
the output does not become a root of the garbage collector, and so
might be deleted by `nix-store --gc`.
- <span id="opt-dry-run">[`--dry-run`](#opt-dry-run)</span>
Show what store paths would be built or downloaded.
- <span id="opt-out-link">[`--out-link`](#opt-out-link)</span> / `-o` *outlink*
Change the name of the symlink to the output path created from
`result` to *outlink*.
{{#include ./status-build-failure.md}}
{{#include ./opt-common.md}}
{{#include ./env-common.md}}
# Examples
```console
$ nix-build '<nixpkgs>' --attr firefox
store derivation is /nix/store/qybprl8sz2lc...-firefox-1.5.0.7.drv
/nix/store/d18hyl92g30l...-firefox-1.5.0.7
$ ls -l result
lrwxrwxrwx ... result -> /nix/store/d18hyl92g30l...-firefox-1.5.0.7
$ ls ./result/bin/
firefox firefox-config
```
If a derivation has multiple outputs, `nix-build` will build the default
(first) output. You can also build all outputs:
```console
$ nix-build '<nixpkgs>' --attr openssl.all
```
This will create a symlink for each output named `result-outputname`.
The suffix is omitted if the output name is `out`. So if `openssl` has
outputs `out`, `bin` and `man`, `nix-build` will create symlinks
`result`, `result-bin` and `result-man`. It’s also possible to build a
specific output:
```console
$ nix-build '<nixpkgs>' --attr openssl.man
```
This will create a symlink `result-man`.
Build a Nix expression given on the command line:
```console
$ nix-build --expr 'with import <nixpkgs> { }; runCommand "foo" { } "echo bar > $out"'
$ cat ./result
bar
```
Build the GNU Hello package from the latest revision of the master
branch of Nixpkgs:
```console
$ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz --attr hello
```

112
doc/manual/source/command-ref/nix-channel.md Normal file
View file

@ -0,0 +1,112 @@
# Name
`nix-channel` - manage Nix channels
# Synopsis
`nix-channel` {`--add` url [*name*] | `--remove` *name* | `--list` | `--update` [*names…*] | `--list-generations` | `--rollback` [*generation*] }
# Description
Channels are a mechanism for referencing remote Nix expressions and conveniently retrieving their latest version.
The moving parts of channels are:
- The official channels listed at <https://nixos.org/channels>
- The user-specific list of [subscribed channels](#subscribed-channels)
- The [downloaded channel contents](#channels)
- The [Nix expression search path](@docroot@/command-ref/conf-file.md#conf-nix-path), set with the [`-I` option](#opt-i) or the [`NIX_PATH` environment variable](#env-NIX_PATH)
> **Note**
>
> The state of a subscribed channel is external to the Nix expressions relying on it.
> This may limit reproducibility.
>
> Dependencies on other Nix expressions can be declared explicitly with:
> - [`fetchurl`](@docroot@/language/builtins.md#builtins-fetchurl), [`fetchTarball`](@docroot@/language/builtins.md#builtins-fetchTarball), or [`fetchGit`](@docroot@/language/builtins.md#builtins-fetchGit) in Nix expressions
> - the [`-I` option](@docroot@/command-ref/opt-common.md#opt-I) in command line invocations
This command has the following operations:
- `--add` *url* \[*name*\]
Add a channel *name* located at *url* to the list of subscribed channels.
If *name* is omitted, default to the last component of *url*, with the suffixes `-stable` or `-unstable` removed.
> **Note**
>
> `--add` does not automatically perform an update.
> Use `--update` explicitly.
A channel URL must point to a directory containing a file `nixexprs.tar.gz`.
At the top level, that tarball must contain a single directory with a `default.nix` file that serves as the channel’s entry point.
- `--remove` *name*
Remove the channel *name* from the list of subscribed channels.
- `--list`
Print the names and URLs of all subscribed channels on standard output.
- `--update` \[*names*…\]
Download the Nix expressions of subscribed channels and create a new generation.
Update all channels if none is specified, and only those included in *names* otherwise.
- `--list-generations`
Prints a list of all the current existing generations for the
channel profile.
Works the same way as
```
nix-env --profile /nix/var/nix/profiles/per-user/$USER/channels --list-generations
```
- `--rollback` \[*generation*\]
Revert channels to the state before the last call to `nix-channel --update`.
Optionally, you can specify a specific channel *generation* number to restore.
{{#include ./opt-common.md}}
{{#include ./env-common.md}}
# Files
`nix-channel` operates on the following files.
{{#include ./files/channels.md}}
# Examples
Subscribe to the Nixpkgs channel and run `hello` from the GNU Hello package:
```console
$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
$ nix-channel --list
nixpkgs https://nixos.org/channels/nixpkgs
$ nix-channel --update
$ nix-shell -p hello --run hello
hello
```
Revert channel updates using `--rollback`:
```console
$ nix-instantiate --eval '<nixpkgs>' --attr lib.version
"22.11pre296212.530a53dcbc9"
$ nix-channel --rollback
switching from generation 483 to 482
$ nix-instantiate --eval '<nixpkgs>' --attr lib.version
"22.11pre281526.d0419badfad"
```
Remove a channel:
```console
$ nix-channel --remove nixpkgs
$ nix-channel --list
```

88
doc/manual/source/command-ref/nix-collect-garbage.md Normal file
View file

@ -0,0 +1,88 @@
# Name
`nix-collect-garbage` - delete unreachable [store objects]
# Synopsis
`nix-collect-garbage` [`--delete-old`] [`-d`] [`--delete-older-than` *period*] [`--max-freed` *bytes*] [`--dry-run`]
# Description
The command `nix-collect-garbage` is mostly an alias of [`nix-store --gc`](@docroot@/command-ref/nix-store/gc.md).
That is, it deletes all unreachable [store objects] in the Nix store to clean up your system.
However, it provides two additional options,
[`--delete-old`](#opt-delete-old) and [`--delete-older-than`](#opt-delete-older-than),
which also delete old [profiles], allowing potentially more [store objects] to be deleted because profiles are also garbage collection roots.
These options are the equivalent of running
[`nix-env --delete-generations`](@docroot@/command-ref/nix-env/delete-generations.md)
with various augments on multiple profiles,
prior to running `nix-collect-garbage` (or just `nix-store --gc`) without any flags.
> **Note**
>
> Deleting previous configurations makes rollbacks to them impossible.
These flags should be used with care, because they potentially delete generations of profiles used by other users on the system.
## Locations searched for profiles
`nix-collect-garbage` cannot know about all profiles; that information doesn't exist.
Instead, it looks in a few locations, and acts on all profiles it finds there:
1. The default profile locations as specified in the [profiles] section of the manual.
2. > **NOTE**
>
> Not stable; subject to change
>
> Do not rely on this functionality; it just exists for migration purposes and may change in the future.
> These deprecated paths remain a private implementation detail of Nix.
`$NIX_STATE_DIR/profiles` and `$NIX_STATE_DIR/profiles/per-user`.
With the exception of `$NIX_STATE_DIR/profiles/per-user/root` and `$NIX_STATE_DIR/profiles/default`, these directories are no longer used by other commands.
`nix-collect-garbage` looks there anyways in order to clean up profiles from older versions of Nix.
# Options
These options are for deleting old [profiles] prior to deleting unreachable [store objects].
- <span id="opt-delete-old">[`--delete-old`](#opt-delete-old)</span> / `-d`
Delete all old generations of profiles.
This is the equivalent of invoking [`nix-env --delete-generations old`](@docroot@/command-ref/nix-env/delete-generations.md#generations-old) on each found profile.
- <span id="opt-delete-older-than">[`--delete-older-than`](#opt-delete-older-than)</span> *period*
Delete all generations of profiles older than the specified amount (except for the generations that were active at that point in time).
*period* is a value such as `30d`, which would mean 30 days.
This is the equivalent of invoking [`nix-env --delete-generations <period>`](@docroot@/command-ref/nix-env/delete-generations.md#generations-time) on each found profile.
See the documentation of that command for additional information about the *period* argument.
- <span id="opt-max-freed">[`--max-freed`](#opt-max-freed)</span> *bytes*
<!-- duplication from https://github.com/NixOS/nix/blob/442a2623e48357ff72c77bb11cf2cf06d94d2f90/doc/manual/source/command-ref/nix-store/gc.md?plain=1#L39-L44 -->
Keep deleting paths until at least *bytes* bytes have been deleted,
then stop. The argument *bytes* can be followed by the
multiplicative suffix `K`, `M`, `G` or `T`, denoting KiB, MiB, GiB
or TiB units.
{{#include ./opt-common.md}}
{{#include ./env-common.md}}
# Example
To delete from the Nix store everything that is not used by the current
generations of each profile, do
```console
$ nix-collect-garbage -d
```
[profiles]: @docroot@/command-ref/files/profiles.md
[store objects]: @docroot@/store/store-object.md

91
doc/manual/source/command-ref/nix-copy-closure.md Normal file
View file

@ -0,0 +1,91 @@
# Name
`nix-copy-closure` - copy store objects to or from a remote machine via SSH
# Synopsis
`nix-copy-closure`
[`--to` | `--from` ]
[`--gzip`]
[`--include-outputs`]
[`--use-substitutes` | `-s`]
[`-v`]
[_user_@]_machine_[:_port_] _paths_
# Description
Given _paths_ from one machine, `nix-copy-closure` computes the [closure](@docroot@/glossary.md#gloss-closure) of those paths (i.e. all their dependencies in the Nix store), and copies [store objects](@docroot@/glossary.md#gloss-store-object) in that closure to another machine via SSH.
It doesn’t copy store objects that are already present on the other machine.
> **Note**
>
> While the Nix store to use on the local machine can be specified on the command line with the [`--store`](@docroot@/command-ref/conf-file.md#conf-store) option, the Nix store to be accessed on the remote machine can only be [configured statically](@docroot@/command-ref/conf-file.md#configuration-file) on that remote machine.
Since `nix-copy-closure` calls `ssh`, you may need to authenticate with the remote machine.
In fact, you may be asked for authentication _twice_ because `nix-copy-closure` currently connects twice to the remote machine: first to get the set of paths missing on the target machine, and second to send the dump of those paths.
When using public key authentication, you can avoid typing the passphrase with `ssh-agent`.
# Options
- `--to`
Copy the closure of _paths_ from a Nix store accessible from the local machine to the Nix store on the remote _machine_.
This is the default behavior.
- `--from`
Copy the closure of _paths_ from the Nix store on the remote _machine_ to the local machine's specified Nix store.
- `--gzip`
Enable compression of the SSH connection.
- `--include-outputs`
Also copy the outputs of [store derivation]s included in the closure.
[store derivation]: @docroot@/glossary.md#gloss-store-derivation
- `--use-substitutes` / `-s`
Attempt to download missing store objects on the target from [substituters](@docroot@/command-ref/conf-file.md#conf-substituters).
Any store objects that cannot be substituted on the target are still copied normally from the source.
This is useful, for instance, if the connection between the source and target machine is slow, but the connection between the target machine and `cache.nixos.org` (the default binary cache server) is fast.
{{#include ./opt-common.md}}
# Environment variables
- `NIX_SSHOPTS`
Additional options to be passed to `ssh` on the command line.
{{#include ./env-common.md}}
# Examples
> **Example**
>
> Copy GNU Hello with all its dependencies to a remote machine:
>
> ```shell-session
> $ storePath="$(nix-build '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello --no-out-link)"
> $ nix-copy-closure --to alice@itchy.example.org "$storePath"
> copying 5 paths...
> copying path '/nix/store/nrwkk6ak3rgkrxbqhsscb01jpzmslf2r-xgcc-13.2.0-libgcc' to 'ssh://alice@itchy.example.org'...
> copying path '/nix/store/gm61h1y42pqyl6178g90x8zm22n6pyy5-libunistring-1.1' to 'ssh://alice@itchy.example.org'...
> copying path '/nix/store/ddfzjdykw67s20c35i7a6624by3iz5jv-libidn2-2.3.7' to 'ssh://alice@itchy.example.org'...
> copying path '/nix/store/apab5i73dqa09wx0q27b6fbhd1r18ihl-glibc-2.39-31' to 'ssh://alice@itchy.example.org'...
> copying path '/nix/store/g1n2vryg06amvcc1avb2mcq36faly0mh-hello-2.12.1' to 'ssh://alice@itchy.example.org'...
> ```
> **Example**
>
> Copy GNU Hello from a remote machine using a known store path, and run it:
>
> ```shell-session
> $ storePath="$(nix-instantiate --eval --raw '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello.outPath)"
> $ nix-copy-closure --from alice@itchy.example.org "$storePath"
> $ "$storePath"/bin/hello
> Hello, world!
> ```

13
doc/manual/source/command-ref/nix-daemon.md Normal file
View file

@ -0,0 +1,13 @@
# Name
`nix-daemon` - Nix multi-user support daemon
# Synopsis
`nix-daemon`
# Description
The Nix daemon is necessary in multi-user Nix installations. It runs
build tasks and other operations on the Nix store on behalf of
unprivileged users.

134
doc/manual/source/command-ref/nix-env.md Normal file
View file

@ -0,0 +1,134 @@
# Name
`nix-env` - manipulate or query Nix user environments
# Synopsis
`nix-env` *operation* [*options*] [*arguments…*]
[`--option` *name* *value*]
[`--arg` *name* *value*]
[`--argstr` *name* *value*]
[{`--file` | `-f`} *path*]
[{`--profile` | `-p`} *path*]
[`--system-filter` *system*]
[`--dry-run`]
# Description
The command `nix-env` is used to manipulate Nix user environments. User
environments are sets of software packages available to a user at some
point in time. In other words, they are a synthesised view of the
programs available in the Nix store. There may be many user
environments: different users can have different environments, and
individual users can switch between different environments.
`nix-env` takes exactly one *operation* flag which indicates the
subcommand to be performed. The following operations are available:
- [`--install`](./nix-env/install.md)
- [`--upgrade`](./nix-env/upgrade.md)
- [`--uninstall`](./nix-env/uninstall.md)
- [`--set`](./nix-env/set.md)
- [`--set-flag`](./nix-env/set-flag.md)
- [`--query`](./nix-env/query.md)
- [`--switch-profile`](./nix-env/switch-profile.md)
- [`--list-generations`](./nix-env/list-generations.md)
- [`--delete-generations`](./nix-env/delete-generations.md)
- [`--switch-generation`](./nix-env/switch-generation.md)
- [`--rollback`](./nix-env/rollback.md)
These pages can be viewed offline:
- `man nix-env-<operation>`.
Example: `man nix-env-install`
- `nix-env --help --<operation>`
Example: `nix-env --help --install`
# Package sources
`nix-env` can obtain packages from multiple sources:
- An attribute set of derivations from:
- The [default Nix expression](@docroot@/command-ref/files/default-nix-expression.md) (by default)
- A Nix file, specified via `--file`
- A [profile](@docroot@/command-ref/files/profiles.md), specified via `--from-profile`
- A Nix expression that is a function which takes default expression as argument, specified via `--from-expression`
- A [store path](@docroot@/store/store-path.md)
# Selectors
Several operations, such as [`nix-env --query`](./nix-env/query.md) and [`nix-env --install`](./nix-env/install.md), take a list of *arguments* that specify the packages on which to operate.
Packages are identified based on a `name` part and a `version` part of a [symbolic derivation name](@docroot@/language/derivations.md#attr-name):
- `name`: Everything up to but not including the first dash (`-`) that is *not* followed by a letter.
- `version`: The rest, excluding the separating dash.
> **Example**
>
> `nix-env` parses the symbolic derivation name `apache-httpd-2.0.48` as:
>
> ```json
> {
> "name": "apache-httpd",
> "version": "2.0.48"
> }
> ```
> **Example**
>
> `nix-env` parses the symbolic derivation name `firefox.*` as:
>
> ```json
> {
> "name": "firefox.*",
> "version": ""
> }
> ```
The `name` parts of the *arguments* to `nix-env` are treated as extended regular expressions and matched against the `name` parts of derivation names in the package source.
The match is case-sensitive.
The regular expression can optionally be followed by a dash (`-`) and a version number; if omitted, any version of the package will match.
For details on regular expressions, see [**regex**(7)](https://linux.die.net/man/7/regex).
> **Example**
>
> Common patterns for finding package names with `nix-env`:
>
> - `firefox`
>
> Matches the package name `firefox` and any version.
>
> - `firefox-32.0`
>
> Matches the package name `firefox` and version `32.0`.
>
> - `gtk\\+`
>
> Matches the package name `gtk+`.
> The `+` character must be escaped using a backslash (`\`) to prevent it from being interpreted as a quantifier, and the backslash must be escaped in turn with another backslash to ensure that the shell passes it on.
>
> - `.\*`
>
> Matches any package name.
> This is the default for most commands.
>
> - `'.*zip.*'`
>
> Matches any package name containing the string `zip`.
> Note the dots: `'*zip*'` does not work, because in a regular expression, the character `*` is interpreted as a quantifier.
>
> - `'.*(firefox|chromium).*'`
>
> Matches any package name containing the strings `firefox` or `chromium`.
# Files
`nix-env` operates on the following files.
{{#include ./files/default-nix-expression.md}}
{{#include ./files/profiles.md}}

98
doc/manual/source/command-ref/nix-env/delete-generations.md Normal file
View file

@ -0,0 +1,98 @@
# Name
`nix-env --delete-generations` - delete profile generations
# Synopsis
`nix-env` `--delete-generations` *generations*
# Description
This operation deletes the specified generations of the current profile.
*generations* can be a one of the following:
- <span id="generations-list">[`<number>...`](#generations-list)</span>
A list of generation numbers, each one a separate command-line argument.
Delete exactly the profile generations given by their generation number.
Deleting the current generation is not allowed.
- <span id="generations-old">[The special value `old`](#generations-old)</span>
Delete all generations except the current one.
> **WARNING**
>
> Older *and newer* generations will be deleted by this operation.
>
> One might expect this to just delete older generations than the curent one, but that is only true if the current generation is also the latest.
> Because one can roll back to a previous generation, it is possible to have generations newer than the current one.
> They will also be deleted.
- <span id="generations-time">[`<number>d`](#generations-time)</span>
The last *number* days
*Example*: `30d`
Delete all generations created more than *number* days ago, except the most recent one of them.
This allows rolling back to generations that were available within the specified period.
- <span id="generations-count">[`+<number>`](#generations-count)</span>
The last *number* generations up to the present
*Example*: `+5`
Keep the last *number* generations, along with any newer than current.
Periodically deleting old generations is important to make garbage collection
effective.
The is because profiles are also garbage collection roots — any [store object] reachable from a profile is "alive" and ineligible for deletion.
[store object]: @docroot@/store/store-object.md
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
# Examples
## Delete explicit generation numbers
```console
$ nix-env --delete-generations 3 4 8
```
Delete the generations numbered 3, 4, and 8, so long as the current active generation is not any of those.
## Keep most-recent by count (number of generations)
```console
$ nix-env --delete-generations +5
```
Suppose `30` is the current generation, and we currently have generations numbered `20` through `32`.
Then this command will delete generations `20` through `25` (`<= 30 - 5`),
and keep generations `26` through `31` (`> 30 - 5`).
## Keep most-recent by time (number of days)
```console
$ nix-env --delete-generations 30d
```
This command will delete all generations older than 30 days, except for the generation that was active 30 days ago (if it currently exists).
## Delete all older
```console
$ nix-env --profile other_profile --delete-generations old
```

7
doc/manual/source/command-ref/nix-env/env-common.md Normal file
View file

@ -0,0 +1,7 @@
# Environment variables
- `NIX_PROFILE`
Location of the Nix profile. Defaults to the target of the symlink
`~/.nix-profile`, if it exists, or `/nix/var/nix/profiles/default`
otherwise.

242
doc/manual/source/command-ref/nix-env/install.md Normal file
View file

@ -0,0 +1,242 @@
# Name
`nix-env --install` - add packages to user environment
# Synopsis
`nix-env` {`--install` | `-i`} *args…*
[{`--prebuilt-only` | `-b`}]
[{`--attr` | `-A`}]
[`--from-expression`] [`-E`]
[`--from-profile` *path*]
[`--preserve-installed` | `-P`]
[`--remove-all` | `-r`]
[`--priority` *priority*]
# Description
The `--install` operation creates a new user environment.
It is based on the current generation of the active [profile](@docroot@/command-ref/files/profiles.md), to which a set of [store paths] described by *args* is added.
[store paths]: @docroot@/store/store-path.md
The arguments *args* map to store paths in a number of possible ways:
- By default, *args* is a set of [derivation] names denoting derivations in the [default Nix expression].
These are [realised], and the resulting output paths are installed.
Currently installed derivations with a name equal to the name of a derivation being added are removed unless the option `--preserve-installed` is specified.
[derivation]: @docroot@/glossary.md#gloss-derivation
[default Nix expression]: @docroot@/command-ref/files/default-nix-expression.md
[realised]: @docroot@/glossary.md#gloss-realise
If there are multiple derivations matching a name in *args* that
have the same name (e.g., `gcc-3.3.6` and `gcc-4.1.1`), then the
derivation with the highest *priority* is used. A derivation can
define a priority by declaring the `meta.priority` attribute. This
attribute should be a number, with a higher value denoting a lower
priority. The default priority is `5`.
If there are multiple matching derivations with the same priority,
then the derivation with the highest version will be installed.
You can force the installation of multiple derivations with the same
name by being specific about the versions. For instance, `nix-env --install
gcc-3.3.6 gcc-4.1.1` will install both version of GCC (and will
probably cause a user environment conflict\!).
- If [`--attr`](#opt-attr) / `-A` is specified, the arguments are *attribute paths* that select attributes from the [default Nix expression].
This is faster than using derivation names and unambiguous.
Show the attribute paths of available packages with [`nix-env --query`](./query.md):
```console
nix-env --query --available --attr-path
```
- If `--from-profile` *path* is given, *args* is a set of names
denoting installed [store paths] in the profile *path*. This is an
easy way to copy user environment elements from one profile to
another.
- If `--from-expression` is given, *args* are [Nix language functions](@docroot@/language/syntax.md#functions) that are called with the [default Nix expression] as their single argument.
The derivations returned by those function calls are installed.
This allows derivations to be specified in an unambiguous way, which is necessary if there are multiple derivations with the same name.
- If `--priority` *priority* is given, the priority of the derivations being installed is set to *priority*.
This can be used to override the priority of the derivations being installed.
This is useful if *args* are [store paths], which don't have any priority information.
- If *args* are [store derivations](@docroot@/glossary.md#gloss-store-derivation), then these are [realised], and the resulting output paths are installed.
- If *args* are [store paths] that are not store derivations, then these are [realised] and installed.
- By default all [outputs](@docroot@/language/derivations.md#attr-outputs) are installed for each [derivation].
This can be overridden by adding a `meta.outputsToInstall` attribute on the derivation listing a subset of the output names.
Example:
The file `example.nix` defines a derivation with two outputs `foo` and `bar`, each containing a file.
```nix
# example.nix
let
pkgs = import <nixpkgs> {};
command = ''
${pkgs.coreutils}/bin/mkdir -p $foo $bar
echo foo > $foo/foo-file
echo bar > $bar/bar-file
'';
in
derivation {
name = "example";
builder = "${pkgs.bash}/bin/bash";
args = [ "-c" command ];
outputs = [ "foo" "bar" ];
system = builtins.currentSystem;
}
```
Installing from this Nix expression will make files from both outputs appear in the current profile.
```console
$ nix-env --install --file example.nix
installing 'example'
$ ls ~/.nix-profile
foo-file
bar-file
manifest.nix
```
Adding `meta.outputsToInstall` to that derivation will make `nix-env` only install files from the specified outputs.
```nix
# example-outputs.nix
import ./example.nix // { meta.outputsToInstall = [ "bar" ]; }
```
```console
$ nix-env --install --file example-outputs.nix
installing 'example'
$ ls ~/.nix-profile
bar-file
manifest.nix
```
# Options
- `--prebuilt-only` / `-b`
Use only derivations for which a substitute is registered, i.e.,
there is a pre-built binary available that can be downloaded in lieu
of building the derivation. Thus, no packages will be built from
source.
- `--preserve-installed` / `-P`
Do not remove derivations with a name matching one of the
derivations being installed. Usually, trying to have two versions of
the same package installed in the same generation of a profile will
lead to an error in building the generation, due to file name
clashes between the two versions. However, this is not the case for
all packages.
- `--remove-all` / `-r`
Remove all previously installed packages first. This is equivalent
to running `nix-env --uninstall '.*'` first, except that everything happens
in a single transaction.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
# Examples
To install a package using a specific attribute path from the active Nix expression:
```console
$ nix-env --install --attr gcc40mips
installing `gcc-4.0.2'
$ nix-env --install --attr xorg.xorgserver
installing `xorg-server-1.2.0'
```
To install a specific version of `gcc` using the derivation name:
```console
$ nix-env --install gcc-3.3.2
installing `gcc-3.3.2'
uninstalling `gcc-3.1'
```
Using attribute path for selecting a package is preferred,
as it is much faster and there will not be multiple matches.
Note the previously installed version is removed, since
`--preserve-installed` was not specified.
To install an arbitrary version:
```console
$ nix-env --install gcc
installing `gcc-3.3.2'
```
To install all derivations in the Nix expression `foo.nix`:
```console
$ nix-env --file ~/foo.nix --install '.*'
```
To copy the store path with symbolic name `gcc` from another profile:
```console
$ nix-env --install --from-profile /nix/var/nix/profiles/foo gcc
```
To install a specific [store derivation] (typically created by
`nix-instantiate`):
```console
$ nix-env --install /nix/store/fibjb1bfbpm5mrsxc4mh2d8n37sxh91i-gcc-3.4.3.drv
```
To install a specific output path:
```console
$ nix-env --install /nix/store/y3cgx0xj1p4iv9x0pnnmdhr8iyg741vk-gcc-3.4.3
```
To install from a Nix expression specified on the command-line:
```console
$ nix-env --file ./foo.nix --install --expr \
'f: (f {system = "i686-linux";}).subversionWithJava'
```
I.e., this evaluates to `(f: (f {system =
"i686-linux";}).subversionWithJava) (import ./foo.nix)`, thus selecting
the `subversionWithJava` attribute from the set returned by calling the
function defined in `./foo.nix`.
A dry-run tells you which paths will be downloaded or built from source:
```console
$ nix-env --file '<nixpkgs>' --install --attr hello --dry-run
(dry run; not doing anything)
installing ‘hello-2.10’
this path will be fetched (0.04 MiB download, 0.19 MiB unpacked):
/nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10
...
```
To install Firefox from the latest revision in the Nixpkgs/NixOS 14.12
channel:
```console
$ nix-env --file https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz --install --attr firefox
```

33
doc/manual/source/command-ref/nix-env/list-generations.md Normal file
View file

@ -0,0 +1,33 @@
# Name
`nix-env --list-generations` - list profile generations
# Synopsis
`nix-env` `--list-generations`
# Description
This operation print a list of all the currently existing generations
for the active profile. These may be switched to using the
`--switch-generation` operation. It also prints the creation date of the
generation, and indicates the current generation.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
# Examples
```console
$ nix-env --list-generations
95 2004-02-06 11:48:24
96 2004-02-06 11:49:01
97 2004-02-06 16:22:45
98 2004-02-06 16:24:33 (current)
```

38
doc/manual/source/command-ref/nix-env/opt-common.md Normal file
View file

@ -0,0 +1,38 @@
# Options
The following options are allowed for all `nix-env` operations, but may not always have an effect.
- `--file` / `-f` *path*
Specifies the Nix expression (designated below as the *active Nix
expression*) used by the `--install`, `--upgrade`, and `--query
--available` operations to obtain derivations. The default is
`~/.nix-defexpr`.
If the argument starts with `http://` or `https://`, it is
interpreted as the URL of a tarball that will be downloaded and
unpacked to a temporary location. The tarball must include a single
top-level directory containing at least a file named `default.nix`.
- `--profile` / `-p` *path*
Specifies the profile to be used by those operations that operate on
a profile (designated below as the *active profile*). A profile is a
sequence of user environments called *generations*, one of which is
the *current generation*.
- `--dry-run`
For the `--install`, `--upgrade`, `--uninstall`,
`--switch-generation`, `--delete-generations` and `--rollback`
operations, this flag will cause `nix-env` to print what *would* be
done if this flag had not been specified, without actually doing it.
`--dry-run` also prints out which paths will be
[substituted](@docroot@/glossary.md) (i.e., downloaded) and which paths
will be built from source (because no substitute is available).
- `--system-filter` *system*
By default, operations such as `--query --available` show derivations matching any platform. This option
allows you to use derivations for the specified platform *system*.

233
doc/manual/source/command-ref/nix-env/query.md Normal file
View file

@ -0,0 +1,233 @@
# Name
`nix-env --query` - display information about packages
# Synopsis
`nix-env` {`--query` | `-q`} *names…*
[`--installed` | `--available` | `-a`]
[{`--status` | `-s`}]
[{`--attr-path` | `-P`}]
[`--no-name`]
[{`--compare-versions` | `-c`}]
[`--system`]
[`--drv-path`]
[`--out-path`]
[`--description`]
[`--meta`]
[`--xml`]
[`--json`]
[{`--prebuilt-only` | `-b`}]
[{`--attr` | `-A`} *attribute-path*]
# Description
The query operation displays information about either the store paths
that are installed in the current generation of the active profile
(`--installed`), or the derivations that are available for installation
in the active Nix expression (`--available`). It only prints information
about derivations whose symbolic name matches one of *names*.
The derivations are sorted by their `name` attributes.
# Source selection
The following flags specify the set of things on which the query
operates.
- `--installed`
The query operates on the store paths that are installed in the
current generation of the active profile. This is the default.
- `--available` / `-a`
The query operates on the derivations that are available in the
active Nix expression.
# Queries
The following flags specify what information to display about the
selected derivations. Multiple flags may be specified, in which case the
information is shown in the order given here. Note that the name of the
derivation is shown unless `--no-name` is specified.
- `--xml`
Print the result in an XML representation suitable for automatic
processing by other tools. The root element is called `items`, which
contains a `item` element for each available or installed
derivation. The fields discussed below are all stored in attributes
of the `item` elements.
- `--json`
Print the result in a JSON representation suitable for automatic
processing by other tools.
- `--prebuilt-only` / `-b`
Show only derivations for which a substitute is registered, i.e.,
there is a pre-built binary available that can be downloaded in lieu
of building the derivation. Thus, this shows all packages that
probably can be installed quickly.
- `--status` / `-s`
Print the *status* of the derivation. The status consists of three
characters. The first is `I` or `-`, indicating whether the
derivation is currently installed in the current generation of the
active profile. This is by definition the case for `--installed`,
but not for `--available`. The second is `P` or `-`, indicating
whether the derivation is present on the system. This indicates
whether installation of an available derivation will require the
derivation to be built. The third is `S` or `-`, indicating whether
a substitute is available for the derivation.
- `--attr-path` / `-P`
Print the *attribute path* of the derivation, which can be used to
unambiguously select it using the `--attr` option available in
commands that install derivations like `nix-env --install`. This
option only works together with `--available`
- `--no-name`
Suppress printing of the `name` attribute of each derivation.
- `--compare-versions` / `-c`
Compare installed versions to available versions, or vice versa (if
`--available` is given). This is useful for quickly seeing whether
upgrades for installed packages are available in a Nix expression. A
column is added with the following meaning:
- `<` *version*
A newer version of the package is available or installed.
- `=` *version*
At most the same version of the package is available or
installed.
- `>` *version*
Only older versions of the package are available or installed.
- `- ?`
No version of the package is available or installed.
- `--system`
Print the `system` attribute of the derivation.
- `--drv-path`
Print the path of the [store derivation](@docroot@/glossary.md#gloss-store-derivation).
- `--out-path`
Print the output path of the derivation.
- `--description`
Print a short (one-line) description of the derivation, if
available. The description is taken from the `meta.description`
attribute of the derivation.
- `--meta`
Print all of the meta-attributes of the derivation. This option is
only available with `--xml` or `--json`.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
# Examples
To show installed packages:
```console
$ nix-env --query
bison-1.875c
docbook-xml-4.2
firefox-1.0.4
MPlayer-1.0pre7
ORBit2-2.8.3
…
```
To show available packages:
```console
$ nix-env --query --available
firefox-1.0.7
GConf-2.4.0.1
MPlayer-1.0pre7
ORBit2-2.8.3
…
```
To show the status of available packages:
```console
$ nix-env --query --available --status
-P- firefox-1.0.7 (not installed but present)
--S GConf-2.4.0.1 (not present, but there is a substitute for fast installation)
--S MPlayer-1.0pre3 (i.e., this is not the installed MPlayer, even though the version is the same!)
IP- ORBit2-2.8.3 (installed and by definition present)
…
```
To show available packages in the Nix expression `foo.nix`:
```console
$ nix-env --file ./foo.nix --query --available
foo-1.2.3
```
To compare installed versions to what’s available:
```console
$ nix-env --query --compare-versions
...
acrobat-reader-7.0 - ? (package is not available at all)
autoconf-2.59 = 2.59 (same version)
firefox-1.0.4 < 1.0.7 (a more recent version is available)
...
```
To show all packages with “`zip`” in the name:
```console
$ nix-env --query --available '.*zip.*'
bzip2-1.0.6
gzip-1.6
zip-3.0
…
```
To show all packages with “`firefox`” or “`chromium`” in the name:
```console
$ nix-env --query --available '.*(firefox|chromium).*'
chromium-37.0.2062.94
chromium-beta-38.0.2125.24
firefox-32.0.3
firefox-with-plugins-13.0.1
…
```
To show all packages in the latest revision of the Nixpkgs repository:
```console
$ nix-env --file https://github.com/NixOS/nixpkgs/archive/master.tar.gz --query --available
```

34
doc/manual/source/command-ref/nix-env/rollback.md Normal file
View file

@ -0,0 +1,34 @@
# Name
`nix-env --rollback` - set user environment to previous generation
# Synopsis
`nix-env` `--rollback`
# Description
This operation switches to the “previous” generation of the active
profile, that is, the highest numbered generation lower than the current
generation, if it exists. It is just a convenience wrapper around
`--list-generations` and `--switch-generation`.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
# Examples
```console
$ nix-env --rollback
switching from generation 92 to 91
```
```console
$ nix-env --rollback
error: no generation older than the current (91) exists
```

82
doc/manual/source/command-ref/nix-env/set-flag.md Normal file
View file

@ -0,0 +1,82 @@
# Name
`nix-env --set-flag` - modify meta attributes of installed packages
# Synopsis
`nix-env` `--set-flag` *name* *value* *drvnames*
# Description
The `--set-flag` operation allows meta attributes of installed packages
to be modified. There are several attributes that can be usefully
modified, because they affect the behaviour of `nix-env` or the user
environment build script:
- `priority` can be changed to resolve filename clashes. The user
environment build script uses the `meta.priority` attribute of
derivations to resolve filename collisions between packages. Lower
priority values denote a higher priority. For instance, the GCC
wrapper package and the Binutils package in Nixpkgs both have a file
`bin/ld`, so previously if you tried to install both you would get a
collision. Now, on the other hand, the GCC wrapper declares a higher
priority than Binutils, so the former’s `bin/ld` is symlinked in the
user environment.
- `keep` can be set to `true` to prevent the package from being
upgraded or replaced. This is useful if you want to hang on to an
older version of a package.
- `active` can be set to `false` to “disable” the package. That is, no
symlinks will be generated to the files of the package, but it
remains part of the profile (so it won’t be garbage-collected). It
can be set back to `true` to re-enable the package.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Examples
To prevent the currently installed Firefox from being upgraded:
```console
$ nix-env --set-flag keep true firefox
```
After this, `nix-env --upgrade ` will ignore Firefox.
To disable the currently installed Firefox, then install a new Firefox
while the old remains part of the profile:
```console
$ nix-env --query
firefox-2.0.0.9 (the current one)
$ nix-env --preserve-installed --install firefox-2.0.0.11
installing `firefox-2.0.0.11'
building path(s) `/nix/store/myy0y59q3ig70dgq37jqwg1j0rsapzsl-user-environment'
collision between `/nix/store/...-firefox-2.0.0.11/bin/firefox'
and `/nix/store/...-firefox-2.0.0.9/bin/firefox'.
(i.e., can’t have two active at the same time)
$ nix-env --set-flag active false firefox
setting flag on `firefox-2.0.0.9'
$ nix-env --preserve-installed --install firefox-2.0.0.11
installing `firefox-2.0.0.11'
$ nix-env --query
firefox-2.0.0.11 (the enabled one)
firefox-2.0.0.9 (the disabled one)
```
To make files from `binutils` take precedence over files from `gcc`:
```console
$ nix-env --set-flag priority 5 binutils
$ nix-env --set-flag priority 10 gcc
```

30
doc/manual/source/command-ref/nix-env/set.md Normal file
View file

@ -0,0 +1,30 @@
# Name
`nix-env --set` - set profile to contain a specified derivation
## Synopsis
`nix-env` `--set` *drvname*
## Description
The `--set` operation modifies the current generation of a profile so
that it contains exactly the specified derivation, and nothing else.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
## Examples
The following updates a profile such that its current generation will
contain just Firefox:
```console
$ nix-env --profile /nix/var/nix/profiles/browser --set firefox
```

33
doc/manual/source/command-ref/nix-env/switch-generation.md Normal file
View file

@ -0,0 +1,33 @@
# Name
`nix-env --switch-generation` - set user environment to given profile generation
# Synopsis
`nix-env` {`--switch-generation` | `-G`} *generation*
# Description
This operation makes generation number *generation* the current
generation of the active profile. That is, if the `profile` is the path
to the active profile, then the symlink `profile` is made to point to
`profile-generation-link`, which is in turn a symlink to the actual user
environment in the Nix store.
Switching will fail if the specified generation does not exist.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
# Examples
```console
$ nix-env --switch-generation 42
switching from generation 50 to 42
```

26
doc/manual/source/command-ref/nix-env/switch-profile.md Normal file
View file

@ -0,0 +1,26 @@
# Name
`nix-env --switch-profile` - set user environment to given profile
# Synopsis
`nix-env` {`--switch-profile` | `-S`} *path*
# Description
This operation makes *path* the current profile for the user. That is,
the symlink `~/.nix-profile` is made to point to *path*.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
# Examples
```console
$ nix-env --switch-profile ~/my-profile
```

28
doc/manual/source/command-ref/nix-env/uninstall.md Normal file
View file

@ -0,0 +1,28 @@
# Name
`nix-env --uninstall` - remove packages from user environment
# Synopsis
`nix-env` {`--uninstall` | `-e`} *drvnames…*
# Description
The uninstall operation creates a new user environment, based on the
current generation of the active profile, from which the store paths
designated by the symbolic names *drvnames* are removed.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
# Examples
```console
$ nix-env --uninstall gcc
$ nix-env --uninstall '.*' (remove everything)
```

147
doc/manual/source/command-ref/nix-env/upgrade.md Normal file
View file

@ -0,0 +1,147 @@
# Name
`nix-env --upgrade` - upgrade packages in user environment
# Synopsis
`nix-env` {`--upgrade` | `-u`} *args*
[`--lt` | `--leq` | `--eq` | `--always`]
[{`--prebuilt-only` | `-b`}]
[{`--attr` | `-A`}]
[`--from-expression`] [`-E`]
[`--from-profile` *path*]
[`--preserve-installed` | `-P`]
# Description
The upgrade operation creates a new user environment, based on the
current generation of the active profile, in which all store paths are
replaced for which there are newer versions in the set of paths
described by *args*. Paths for which there are no newer versions are
left untouched; this is not an error. It is also not an error if an
element of *args* matches no installed derivations.
For a description of how *args* is mapped to a set of store paths, see
[`--install`](#operation---install). If *args* describes multiple
store paths with the same symbolic name, only the one with the highest
version is installed.
# Flags
- `--lt`
Only upgrade a derivation to newer versions. This is the default.
- `--leq`
In addition to upgrading to newer versions, also “upgrade” to
derivations that have the same version. Version are not a unique
identification of a derivation, so there may be many derivations
that have the same version. This flag may be useful to force
“synchronisation” between the installed and available derivations.
- `--eq`
*Only* “upgrade” to derivations that have the same version. This may
not seem very useful, but it actually is, e.g., when there is a new
release of Nixpkgs and you want to replace installed applications
with the same versions built against newer dependencies (to reduce
the number of dependencies floating around on your system).
- `--always`
In addition to upgrading to newer versions, also “upgrade” to
derivations that have the same or a lower version. I.e., derivations
may actually be downgraded depending on what is available in the
active Nix expression.
- `--prebuilt-only` / `-b`
Use only derivations for which a substitute is registered, i.e.,
there is a pre-built binary available that can be downloaded in lieu
of building the derivation. Thus, no packages will be built from
source.
- `--preserve-installed` / `-P`
Do not remove derivations with a name matching one of the
derivations being installed. Usually, trying to have two versions of
the same package installed in the same generation of a profile will
lead to an error in building the generation, due to file name
clashes between the two versions. However, this is not the case for
all packages.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ./env-common.md}}
{{#include ../env-common.md}}
# Examples
```console
$ nix-env --upgrade --attr nixpkgs.gcc
upgrading `gcc-3.3.1' to `gcc-3.4'
```
When there are no updates available, nothing will happen:
```console
$ nix-env --upgrade --attr nixpkgs.pan
```
Using `-A` is preferred when possible, as it is faster and unambiguous but
it is also possible to upgrade to a specific version by matching the derivation name:
```console
$ nix-env --upgrade gcc-3.3.2 --always
upgrading `gcc-3.4' to `gcc-3.3.2'
```
To try to upgrade everything
(matching packages based on the part of the derivation name without version):
```console
$ nix-env --upgrade
upgrading `hello-2.1.2' to `hello-2.1.3'
upgrading `mozilla-1.2' to `mozilla-1.4'
```
# Versions
The upgrade operation determines whether a derivation `y` is an upgrade
of a derivation `x` by looking at their respective `name` attributes.
The names (e.g., `gcc-3.3.1` are split into two parts: the package name
(`gcc`), and the version (`3.3.1`). The version part starts after the
first dash not followed by a letter. `y` is considered an upgrade of `x`
if their package names match, and the version of `y` is higher than that
of `x`.
The versions are compared by splitting them into contiguous components
of numbers and letters. E.g., `3.3.1pre5` is split into `[3, 3, 1,
"pre", 5]`. These lists are then compared lexicographically (from left
to right). Corresponding components `a` and `b` are compared as follows.
If they are both numbers, integer comparison is used. If `a` is an empty
string and `b` is a number, `a` is considered less than `b`. The special
string component `pre` (for *pre-release*) is considered to be less than
other components. String components are considered less than number
components. Otherwise, they are compared lexicographically (i.e., using
case-sensitive string comparison).
This is illustrated by the following examples:
1.0 < 2.3
2.1 < 2.3
2.3 = 2.3
2.5 > 2.3
3.1 > 2.3
2.3.1 > 2.3
2.3.1 > 2.3a
2.3pre1 < 2.3
2.3pre3 < 2.3pre12
2.3a < 2.3c
2.3pre1 < 2.3c
2.3pre1 < 2.3q

154
doc/manual/source/command-ref/nix-hash.md Normal file
View file

@ -0,0 +1,154 @@
# Name
`nix-hash` - compute the cryptographic hash of a path
# Synopsis
`nix-hash` [`--flat`] [`--base32`] [`--truncate`] [`--type` *hashAlgo*] *path…*
`nix-hash` [`--to-base16`|`--to-base32`|`--to-base64`|`--to-sri`] [`--type` *hashAlgo*] *hash…*
# Description
The command `nix-hash` computes the cryptographic hash of the contents
of each *path* and prints it on standard output. By default, it computes
an MD5 hash, but other hash algorithms are available as well. The hash
is printed in hexadecimal. To generate the same hash as
`nix-prefetch-url` you have to specify multiple arguments, see below for
an example.
The hash is computed over a *serialisation* of each path: a dump of
the file system tree rooted at the path. This allows directories and
symlinks to be hashed as well as regular files. The dump is in the
*[Nix Archive (NAR)][Nix Archive] format* produced by [`nix-store
--dump`](@docroot@/command-ref/nix-store/dump.md). Thus, `nix-hash path`
yields the same cryptographic hash as `nix-store --dump path |
md5sum`.
[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
# Options
- `--flat`
Print the cryptographic hash of the contents of each regular file *path*.
That is, instead of computing
the hash of the [Nix Archive (NAR)](@docroot@/store/file-system-object/content-address.md#serial-nix-archive) of *path*,
just [directly hash]((@docroot@/store/file-system-object/content-address.md#serial-flat) *path* as is.
This requires *path* to resolve to a regular file rather than directory.
The result is identical to that produced by the GNU commands
`md5sum` and `sha1sum`.
- `--base16`
Print the hash in a hexadecimal representation (default).
- `--base32`
Print the hash in a base-32 representation rather than hexadecimal.
This base-32 representation is more compact and can be used in Nix
expressions (such as in calls to `fetchurl`).
- `--base64`
Similar to --base32, but print the hash in a base-64 representation,
which is more compact than the base-32 one.
- `--sri`
Print the hash in SRI format with base-64 encoding.
The type of hash algorithm will be prepended to the hash string,
followed by a hyphen (-) and the base-64 hash body.
- `--truncate`
Truncate hashes longer than 160 bits (such as SHA-256) to 160 bits.
- `--type` *hashAlgo*
Use the specified cryptographic hash algorithm, which can be one of
`md5`, `sha1`, `sha256`, and `sha512`.
- `--to-base16`
Don’t hash anything, but convert the base-32 hash representation
*hash* to hexadecimal.
- `--to-base32`
Don’t hash anything, but convert the hexadecimal hash representation
*hash* to base-32.
- `--to-base64`
Don’t hash anything, but convert the hexadecimal hash representation
*hash* to base-64.
- `--to-sri`
Don’t hash anything, but convert the hexadecimal hash representation
*hash* to SRI.
# Examples
Computing the same hash as `nix-prefetch-url`:
```console
$ nix-prefetch-url file://<(echo test)
1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
$ nix-hash --type sha256 --flat --base32 <(echo test)
1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
```
Computing hashes:
```console
$ mkdir test
$ echo "hello" > test/world
$ nix-hash test/ (MD5 hash; default)
8179d3caeff1869b5ba1744e5a245c04
$ nix-store --dump test/ | md5sum (for comparison)
8179d3caeff1869b5ba1744e5a245c04 -
$ nix-hash --type sha1 test/
e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
$ nix-hash --type sha1 --base16 test/
e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
$ nix-hash --type sha1 --base32 test/
nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
$ nix-hash --type sha1 --base64 test/
5P2Lpfe76upazon+ECVVNs1g2rY=
$ nix-hash --type sha1 --sri test/
sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
$ nix-hash --type sha256 --flat test/
error: reading file `test/': Is a directory
$ nix-hash --type sha256 --flat test/world
5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03
```
Converting between hexadecimal, base-32, base-64, and SRI:
```console
$ nix-hash --type sha1 --to-base32 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
$ nix-hash --type sha1 --to-base16 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
$ nix-hash --type sha1 --to-base64 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
5P2Lpfe76upazon+ECVVNs1g2rY=
$ nix-hash --type sha1 --to-sri nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
$ nix-hash --to-base16 sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
```

207
doc/manual/source/command-ref/nix-instantiate.md Normal file
View file

@ -0,0 +1,207 @@
# Name
`nix-instantiate` - instantiate store derivations from Nix expressions
# Synopsis
`nix-instantiate`
[`--parse` | `--eval` [`--strict`] [`--raw` | `--json` | `--xml`] ]
[`--read-write-mode`]
[`--arg` *name* *value*]
[{`--attr`| `-A`} *attrPath*]
[`--add-root` *path*]
[`--expr` | `-E`]
*files…*
`nix-instantiate` `--find-file` *files…*
# Description
The command `nix-instantiate` produces [store derivation]s from (high-level) Nix expressions.
It evaluates the Nix expressions in each of *files* (which defaults to
*./default.nix*). Each top-level expression should evaluate to a
derivation, a list of derivations, or a set of derivations. The paths
of the resulting store derivations are printed on standard output.
[store derivation]: @docroot@/glossary.md#gloss-store-derivation
If *files* is the character `-`, then a Nix expression will be read from
standard input.
# Options
- `--add-root` *path*
See the [corresponding option](nix-store.md) in `nix-store`.
- `--parse`
Just parse the input files, and print their abstract syntax trees on
standard output as a Nix expression.
- `--eval`
Just parse and evaluate the input files, and print the resulting
values on standard output. No instantiation of store derivations
takes place.
> **Warning**
>
> This option produces output which can be parsed as a Nix expression which
> will produce a different result than the input expression when evaluated.
> For example, these two Nix expressions print the same result despite
> having different meaning:
>
> ```console
> $ nix-instantiate --eval --expr '{ a = {}; }'
> { a = <CODE>; }
> $ nix-instantiate --eval --expr '{ a = <CODE>; }'
> { a = <CODE>; }
> ```
>
> For human-readable output, `nix eval` (experimental) is more informative:
>
> ```console
> $ nix-instantiate --eval --expr 'a: a'
> <LAMBDA>
> $ nix eval --expr 'a: a'
> «lambda @ «string»:1:1»
> ```
>
> For machine-readable output, the `--xml` option produces unambiguous
> output:
>
> ```console
> $ nix-instantiate --eval --xml --expr '{ foo = <CODE>; }'
> <?xml version='1.0' encoding='utf-8'?>
> <expr>
> <attrs>
> <attr column="3" line="1" name="foo">
> <unevaluated />
> </attr>
> </attrs>
> </expr>
> ```
- `--find-file`
Look up the given files in Nix’s search path (as specified by the
`NIX_PATH` environment variable). If found, print the corresponding
absolute paths on standard output. For instance, if `NIX_PATH` is
`nixpkgs=/home/alice/nixpkgs`, then `nix-instantiate --find-file
nixpkgs/default.nix` will print `/home/alice/nixpkgs/default.nix`.
- `--strict`
When used with `--eval`, recursively evaluate list elements and
attributes. Normally, such sub-expressions are left unevaluated
(since the Nix language is lazy).
> **Warning**
>
> This option can cause non-termination, because lazy data
> structures can be infinitely large.
- `--raw`
When used with `--eval`, the evaluation result must be a string,
which is printed verbatim, without quoting, escaping or trailing newline.
- `--json`
When used with `--eval`, print the resulting value as an JSON
representation of the abstract syntax tree rather than as a Nix expression.
- `--xml`
When used with `--eval`, print the resulting value as an XML
representation of the abstract syntax tree rather than as a Nix expression.
The schema is the same as that used by the [`toXML`
built-in](../language/builtins.md).
- `--read-write-mode`
When used with `--eval`, perform evaluation in read/write mode so
nix language features that require it will still work (at the cost
of needing to do instantiation of every evaluated derivation). If
this option is not enabled, there may be uninstantiated store paths
in the final output.
{{#include ./opt-common.md}}
{{#include ./env-common.md}}
# Examples
Instantiate [store derivation]s from a Nix expression, and build them using `nix-store`:
```console
$ nix-instantiate test.nix (instantiate)
/nix/store/cigxbmvy6dzix98dxxh9b6shg7ar5bvs-perl-BerkeleyDB-0.26.drv
$ nix-store --realise $(nix-instantiate test.nix) (build)
...
/nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26 (output path)
$ ls -l /nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26
dr-xr-xr-x 2 eelco users 4096 1970-01-01 01:00 lib
...
```
You can also give a Nix expression on the command line:
```console
$ nix-instantiate --expr 'with import <nixpkgs> { }; hello'
/nix/store/j8s4zyv75a724q38cb0r87rlczaiag4y-hello-2.8.drv
```
This is equivalent to:
```console
$ nix-instantiate '<nixpkgs>' --attr hello
```
Parsing and evaluating Nix expressions:
```console
$ nix-instantiate --parse --expr '1 + 2'
1 + 2
```
```console
$ nix-instantiate --eval --expr '1 + 2'
3
```
```console
$ nix-instantiate --eval --xml --expr '1 + 2'
<?xml version='1.0' encoding='utf-8'?>
<expr>
<int value="3" />
</expr>
```
The difference between non-strict and strict evaluation:
```console
$ nix-instantiate --eval --xml --expr '{ x = {}; }'
<?xml version='1.0' encoding='utf-8'?>
<expr>
<attrs>
<attr column="3" line="1" name="x">
<unevaluated />
</attr>
</attrs>
</expr>
$ nix-instantiate --eval --xml --strict --expr '{ x = {}; }'
<?xml version='1.0' encoding='utf-8'?>
<expr>
<attrs>
<attr column="3" line="1" name="x">
<attrs>
</attrs>
</attr>
</attrs>
</expr>
```

86
doc/manual/source/command-ref/nix-prefetch-url.md Normal file
View file

@ -0,0 +1,86 @@
# Name
`nix-prefetch-url` - copy a file from a URL into the store and print its hash
# Synopsis
`nix-prefetch-url` *url* [*hash*]
[`--type` *hashAlgo*]
[`--print-path`]
[`--unpack`]
[`--name` *name*]
# Description
The command `nix-prefetch-url` downloads the file referenced by the URL
*url*, prints its cryptographic hash, and copies it into the Nix store.
The file name in the store is `hash-baseName`, where *baseName* is
everything following the final slash in *url*.
This command is just a convenience for Nix expression writers. Often a
Nix expression fetches some source distribution from the network using
the `fetchurl` expression contained in Nixpkgs. However, `fetchurl`
requires a cryptographic hash. If you don't know the hash, you would
have to download the file first, and then `fetchurl` would download it
again when you build your Nix expression. Since `fetchurl` uses the same
name for the downloaded file as `nix-prefetch-url`, the redundant
download can be avoided.
If *hash* is specified, then a download is not performed if the Nix
store already contains a file with the same hash and base name.
Otherwise, the file is downloaded, and an error is signaled if the
actual hash of the file does not match the specified hash.
This command prints the hash on standard output.
The hash is printed using base-32 unless `--type md5` is specified,
in which case it's printed using base-16.
Additionally, if the option `--print-path` is used,
the path of the downloaded file in the Nix store is also printed.
# Options
- `--type` *hashAlgo*
Use the specified cryptographic hash algorithm,
which can be one of `md5`, `sha1`, `sha256`, and `sha512`.
The default is `sha256`.
- `--print-path`
Print the store path of the downloaded file on standard output.
- `--unpack`
Unpack the archive (which must be a tarball or zip file) and add the
result to the Nix store. The resulting hash can be used with
functions such as Nixpkgs’s `fetchzip` or `fetchFromGitHub`.
- `--executable`
Set the executable bit on the downloaded file.
- `--name` *name*
Override the name of the file in the Nix store. By default, this is
`hash-basename`, where *basename* is the last component of *url*.
Overriding the name is necessary when *basename* contains characters
that are not allowed in Nix store paths.
# Examples
```console
$ nix-prefetch-url ftp://ftp.gnu.org/pub/gnu/hello/hello-2.10.tar.gz
0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
```
```console
$ nix-prefetch-url --print-path mirror://gnu/hello/hello-2.10.tar.gz
0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz
```
```console
$ nix-prefetch-url --unpack --print-path https://github.com/NixOS/patchelf/archive/0.8.tar.gz
079agjlv0hrv7fxnx9ngipx14gyncbkllxrp9cccnh3a50fxcmy7
/nix/store/19zrmhm3m40xxaw81c8cqm6aljgrnwj2-0.8.tar.gz
```

325
doc/manual/source/command-ref/nix-shell.md Normal file
View file

@ -0,0 +1,325 @@
# Name
`nix-shell` - start an interactive shell based on a Nix expression
# Synopsis
`nix-shell`
[`--arg` *name* *value*]
[`--argstr` *name* *value*]
[{`--attr` | `-A`} *attrPath*]
[`--command` *cmd*]
[`--run` *cmd*]
[`--exclude` *regexp*]
[`--pure`]
[`--keep` *name*]
{{`--packages` | `-p`} {*packages* | *expressions*} … | [*path*]}
# Disambiguation
This man page describes the command `nix-shell`, which is distinct from `nix
shell`. For documentation on the latter, run `nix shell --help` or see `man
nix3-shell`.
# Description
The command `nix-shell` will build the dependencies of the specified
derivation, but not the derivation itself. It will then start an
interactive shell in which all environment variables defined by the
derivation *path* have been set to their corresponding values, and the
script `$stdenv/setup` has been sourced. This is useful for reproducing
the environment of a derivation for development.
If *path* is not given, `nix-shell` defaults to `shell.nix` if it
exists, and `default.nix` otherwise.
If *path* starts with `http://` or `https://`, it is interpreted as the
URL of a tarball that will be downloaded and unpacked to a temporary
location. The tarball must include a single top-level directory
containing at least a file named `default.nix`.
If the derivation defines the variable `shellHook`, it will be run
after `$stdenv/setup` has been sourced. Since this hook is not executed
by regular Nix builds, it allows you to perform initialisation specific
to `nix-shell`. For example, the derivation attribute
```nix
shellHook =
''
echo "Hello shell"
export SOME_API_TOKEN="$(cat ~/.config/some-app/api-token)"
'';
```
will cause `nix-shell` to print `Hello shell` and set the `SOME_API_TOKEN`
environment variable to a user-configured value.
# Options
All options not listed here are passed to `nix-store
--realise`, except for `--arg` and `--attr` / `-A` which are passed to
`nix-instantiate`.
- `--command` *cmd*
In the environment of the derivation, run the shell command *cmd*.
This command is executed in an interactive shell. (Use `--run` to
use a non-interactive shell instead.) However, a call to `exit` is
implicitly added to the command, so the shell will exit after
running the command. To prevent this, add `return` at the end;
e.g. `--command "echo Hello; return"` will print `Hello` and then
drop you into the interactive shell. This can be useful for doing
any additional initialisation.
- `--run` *cmd*
Like `--command`, but executes the command in a non-interactive
shell. This means (among other things) that if you hit Ctrl-C while
the command is running, the shell exits.
- `--exclude` *regexp*
Do not build any dependencies whose store path matches the regular
expression *regexp*. This option may be specified multiple times.
- `--pure`
If this flag is specified, the environment is almost entirely
cleared before the interactive shell is started, so you get an
environment that more closely corresponds to the “real” Nix build. A
few variables, in particular `HOME`, `USER` and `DISPLAY`, are
retained. Note that the shell used to run commands is obtained from
[`NIX_BUILD_SHELL`](#env-NIX_BUILD_SHELL) / `<nixpkgs>` from
`NIX_PATH`, and therefore not affected by `--pure`.
- `--packages` / `-p` *packages*…
Set up an environment in which the specified packages are present.
The command line arguments are interpreted as attribute names inside
the Nix Packages collection. Thus, `nix-shell --packages libjpeg openjdk`
will start a shell in which the packages denoted by the attribute
names `libjpeg` and `openjdk` are present.
- `-i` *interpreter*
The chained script interpreter to be invoked by `nix-shell`. Only
applicable in `#!`-scripts (described below).
- `--keep` *name*
When a `--pure` shell is started, keep the listed environment
variables.
{{#include ./opt-common.md}}
# Environment variables
- <span id="env-NIX_BUILD_SHELL">[`NIX_BUILD_SHELL`](#env-NIX_BUILD_SHELL)</span>
Shell used to start the interactive environment.
Defaults to the `bash` from `bashInteractive` found in `<nixpkgs>`, falling back to the `bash` found in `PATH` if not found.
> **Note**
>
> The shell obtained using this method may not necessarily be the same as any shells requested in *path*.
<!-- -->
> **Example
>
> Despite `--pure`, this invocation will not result in a fully reproducible shell environment:
>
> ```nix
> #!/usr/bin/env -S nix-shell --pure
> let
> pkgs = import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/854fdc68881791812eddd33b2fed94b954979a8e.tar.gz") {};
> in
> pkgs.mkShell {
> buildInputs = pkgs.bashInteractive;
> }
> ```
{{#include ./env-common.md}}
# Examples
To build the dependencies of the package Pan, and start an interactive
shell in which to build it:
```console
$ nix-shell '<nixpkgs>' --attr pan
[nix-shell]$ eval ${unpackPhase:-unpackPhase}
[nix-shell]$ cd $sourceRoot
[nix-shell]$ eval ${patchPhase:-patchPhase}
[nix-shell]$ eval ${configurePhase:-configurePhase}
[nix-shell]$ eval ${buildPhase:-buildPhase}
[nix-shell]$ ./pan/gui/pan
```
The reason we use form `eval ${configurePhase:-configurePhase}` here is because
those packages that override these phases do so by exporting the overridden
values in the environment variable of the same name.
Here bash is being told to either evaluate the contents of 'configurePhase',
if it exists as a variable, otherwise evaluate the configurePhase function.
To clear the environment first, and do some additional automatic
initialisation of the interactive shell:
```console
$ nix-shell '<nixpkgs>' --attr pan --pure \
--command 'export NIX_DEBUG=1; export NIX_CORES=8; return'
```
Nix expressions can also be given on the command line using the `-E` and
`-p` flags. For instance, the following starts a shell containing the
packages `sqlite` and `libX11`:
```console
$ nix-shell --expr 'with import <nixpkgs> { }; runCommand "dummy" { buildInputs = [ sqlite xorg.libX11 ]; } ""'
```
A shorter way to do the same is:
```console
$ nix-shell --packages sqlite xorg.libX11
[nix-shell]$ echo $NIX_LDFLAGS
… -L/nix/store/j1zg5v…-sqlite-3.8.0.2/lib -L/nix/store/0gmcz9…-libX11-1.6.1/lib …
```
Note that `-p` accepts multiple full nix expressions that are valid in
the `buildInputs = [ ... ]` shown above, not only package names. So the
following is also legal:
```console
$ nix-shell --packages sqlite 'git.override { withManual = false; }'
```
The `-p` flag looks up Nixpkgs in the Nix search path. You can override
it by passing `-I` or setting `NIX_PATH`. For example, the following
gives you a shell containing the Pan package from a specific revision of
Nixpkgs:
```console
$ nix-shell --packages pan -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/8a3eea054838b55aca962c3fbde9c83c102b8bf2.tar.gz
[nix-shell:~]$ pan --version
Pan 0.139
```
# Use as a `#!`-interpreter
You can use `nix-shell` as a script interpreter to allow scripts written
in arbitrary languages to obtain their own dependencies via Nix. This is
done by starting the script with the following lines:
```bash
#! /usr/bin/env nix-shell
#! nix-shell -i real-interpreter --packages packages
```
where *real-interpreter* is the “real” script interpreter that will be
invoked by `nix-shell` after it has obtained the dependencies and
initialised the environment, and *packages* are the attribute names of
the dependencies in Nixpkgs.
The lines starting with `#! nix-shell` specify `nix-shell` options (see
above). Note that you cannot write `#! /usr/bin/env nix-shell -i ...`
because many operating systems only allow one argument in `#!` lines.
For example, here is a Python script that depends on Python and the
`prettytable` package:
```python
#! /usr/bin/env nix-shell
#! nix-shell -i python3 --packages python3 python3Packages.prettytable
import prettytable
# Print a simple table.
t = prettytable.PrettyTable(["N", "N^2"])
for n in range(1, 10): t.add_row([n, n * n])
print(t)
```
Similarly, the following is a Perl script that specifies that it
requires Perl and the `HTML::TokeParser::Simple` and `LWP` packages:
```perl
#! /usr/bin/env nix-shell
#! nix-shell -i perl --packages perl perlPackages.HTMLTokeParserSimple perlPackages.LWP
use HTML::TokeParser::Simple;
# Fetch nixos.org and print all hrefs.
my $p = HTML::TokeParser::Simple->new(url => 'http://nixos.org/');
while (my $token = $p->get_tag("a")) {
my $href = $token->get_attr("href");
print "$href\n" if $href;
}
```
Sometimes you need to pass a simple Nix expression to customize a
package like Terraform:
```bash
#! /usr/bin/env nix-shell
#! nix-shell -i bash --packages 'terraform.withPlugins (plugins: [ plugins.openstack ])'
terraform apply
```
> **Note**
>
> You must use single or double quotes (`'`, `"`) when passing a simple Nix expression
> in a nix-shell shebang.
Finally, using the merging of multiple nix-shell shebangs the following
Haskell script uses a specific branch of Nixpkgs/NixOS (the 20.03 stable
branch):
```haskell
#! /usr/bin/env nix-shell
#! nix-shell -i runghc --packages 'haskellPackages.ghcWithPackages (ps: [ps.download-curl ps.tagsoup])'
#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-20.03.tar.gz
import Network.Curl.Download
import Text.HTML.TagSoup
import Data.Either
import Data.ByteString.Char8 (unpack)
-- Fetch nixos.org and print all hrefs.
main = do
resp <- openURI "https://nixos.org/"
let tags = filter (isTagOpenName "a") $ parseTags $ unpack $ fromRight undefined resp
let tags' = map (fromAttrib "href") tags
mapM_ putStrLn $ filter (/= "") tags'
```
If you want to be even more precise, you can specify a specific revision
of Nixpkgs:
#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/0672315759b3e15e2121365f067c1c8c56bb4722.tar.gz
The examples above all used `-p` to get dependencies from Nixpkgs. You
can also use a Nix expression to build your own dependencies. For
example, the Python example could have been written as:
```python
#! /usr/bin/env nix-shell
#! nix-shell deps.nix -i python
```
where the file `deps.nix` in the same directory as the `#!`-script
contains:
```nix
with import <nixpkgs> {};
runCommand "dummy" { buildInputs = [ python pythonPackages.prettytable ]; } ""
```
The script's file name is passed as the first argument to the interpreter specified by the `-i` flag.
Aside from the very first line, which is a directive to the operating system, the additional `#! nix-shell` lines do not need to be at the beginning of the file.
This allows wrapping them in block comments for languages where `#` does not start a comment, such as ECMAScript, Erlang, PHP, or Ruby.

47
doc/manual/source/command-ref/nix-store.md Normal file
View file

@ -0,0 +1,47 @@
# Name
`nix-store` - manipulate or query the Nix store
# Synopsis
`nix-store` *operation* [*options…*] [*arguments…*]
[`--option` *name* *value*]
[`--add-root` *path*]
# Description
The command `nix-store` performs primitive operations on the Nix store.
You generally do not need to run this command manually.
`nix-store` takes exactly one *operation* flag which indicates the subcommand to be performed. The following operations are available:
- [`--realise`](./nix-store/realise.md)
- [`--serve`](./nix-store/serve.md)
- [`--gc`](./nix-store/gc.md)
- [`--delete`](./nix-store/delete.md)
- [`--query`](./nix-store/query.md)
- [`--add`](./nix-store/add.md)
- [`--add-fixed`](./nix-store/add-fixed.md)
- [`--verify`](./nix-store/verify.md)
- [`--verify-path`](./nix-store/verify-path.md)
- [`--repair-path`](./nix-store/repair-path.md)
- [`--dump`](./nix-store/dump.md)
- [`--restore`](./nix-store/restore.md)
- [`--export`](./nix-store/export.md)
- [`--import`](./nix-store/import.md)
- [`--optimise`](./nix-store/optimise.md)
- [`--read-log`](./nix-store/read-log.md)
- [`--dump-db`](./nix-store/dump-db.md)
- [`--load-db`](./nix-store/load-db.md)
- [`--print-env`](./nix-store/print-env.md)
- [`--generate-binary-cache-key`](./nix-store/generate-binary-cache-key.md)
These pages can be viewed offline:
- `man nix-store-<operation>`.
Example: `man nix-store-realise`
- `nix-store --help --<operation>`
Example: `nix-store --help --realise`

39
doc/manual/source/command-ref/nix-store/add-fixed.md Normal file
View file

@ -0,0 +1,39 @@
# Name
`nix-store --add-fixed` - add paths to store using given hashing algorithm
## Synopsis
`nix-store` `--add-fixed` [`--recursive`] *algorithm* *paths…*
## Description
The operation `--add-fixed` adds the specified paths to the Nix store.
Unlike `--add` paths are registered using the specified hashing
algorithm, resulting in the same output path as a fixed-output
derivation. This can be used for sources that are not available from a
public url or broke since the download expression was written.
This operation has the following options:
- `--recursive`
Use recursive instead of flat hashing mode, used when adding
directories to the store.
*paths* that refer to symlinks are not dereferenced, but added to the store
as symlinks with the same target.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
## Example
```console
$ nix-store --add-fixed sha256 ./hello-2.10.tar.gz
/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz
```

28
doc/manual/source/command-ref/nix-store/add.md Normal file
View file

@ -0,0 +1,28 @@
# Name
`nix-store --add` - add paths to Nix store
# Synopsis
`nix-store` `--add` *paths…*
# Description
The operation `--add` adds the specified paths to the Nix store. It
prints the resulting paths in the Nix store on standard output.
*paths* that refer to symlinks are not dereferenced, but added to the store
as symlinks with the same target.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Example
```console
$ nix-store --add ./foo.c
/nix/store/m7lrha58ph6rcnv109yzx1nk1cj7k7zf-foo.c
```

33
doc/manual/source/command-ref/nix-store/delete.md Normal file
View file

@ -0,0 +1,33 @@
# Name
`nix-store --delete` - delete store paths
# Synopsis
`nix-store` `--delete` [`--ignore-liveness`] *paths…*
# Description
The operation `--delete` deletes the store paths *paths* from the Nix
store, but only if it is safe to do so; that is, when the path is not
reachable from a root of the garbage collector. This means that you can
only delete paths that would also be deleted by `nix-store --gc`. Thus,
`--delete` is a more targeted version of `--gc`.
With the option `--ignore-liveness`, reachability from the roots is
ignored. However, the path still won’t be deleted if there are other
paths in the store that refer to it (i.e., depend on it).
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Example
```console
$ nix-store --delete /nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4
0 bytes freed (0.00 MiB)
error: cannot delete path `/nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4' since it is still alive
```

26
doc/manual/source/command-ref/nix-store/dump-db.md Normal file
View file

@ -0,0 +1,26 @@
# Name
`nix-store --dump-db` - export Nix database
# Synopsis
`nix-store` `--dump-db` [*paths…*]
# Description
The operation `--dump-db` writes a dump of the Nix database to standard
output. It can be loaded into an empty Nix store using `--load-db`. This
is useful for making backups and when migrating to different database
schemas.
By default, `--dump-db` will dump the entire Nix database. When one or
more store paths is passed, only the subset of the Nix database for
those store paths is dumped. As with `--export`, the user is responsible
for passing all the store paths for a closure. See `--export` for an
example.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}

41
doc/manual/source/command-ref/nix-store/dump.md Normal file
View file

@ -0,0 +1,41 @@
# Name
`nix-store --dump` - write a single path to a [Nix Archive]
## Synopsis
`nix-store` `--dump` *path*
## Description
The operation `--dump` produces a [Nix archive](@docroot@/glossary.md#gloss-nar) (NAR) file containing the
contents of the file system tree rooted at *path*. The archive is
written to standard output.
A NAR archive is like a TAR or Zip archive, but it contains only the
information that Nix considers important. For instance, timestamps are
elided because all files in the Nix store have their timestamp set to 0
anyway. Likewise, all permissions are left out except for the execute
bit, because all files in the Nix store have 444 or 555 permission.
Also, a NAR archive is *canonical*, meaning that “equal” paths always
produce the same NAR archive. For instance, directory entries are
always sorted so that the actual on-disk order doesn’t influence the
result. This means that the cryptographic hash of a NAR dump of a
path is usable as a fingerprint of the contents of the path. Indeed,
the hashes of store paths stored in Nix’s database (see `nix-store --query
--hash`) are SHA-256 hashes of the NAR dump of each store path.
NAR archives support filenames of unlimited length and 64-bit file
sizes. They can contain regular files, directories, and symbolic links,
but not other types of files (such as device nodes).
A Nix archive can be unpacked using [`nix-store --restore`](@docroot@/command-ref/nix-store/restore.md).
[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}

53
doc/manual/source/command-ref/nix-store/export.md Normal file
View file

@ -0,0 +1,53 @@
# Name
`nix-store --export` - export store paths to a [Nix Archive]
## Synopsis
`nix-store` `--export` *paths…*
## Description
The operation `--export` writes a serialisation of the given [store objects](@docroot@/glossary.md#gloss-store-object) to standard output in a format that can be imported into another [Nix store](@docroot@/store/index.md) with [`nix-store --import`](./import.md).
> **Warning**
>
> This command *does not* produce a [closure](@docroot@/glossary.md#gloss-closure) of the specified store paths.
> Trying to import a store object that refers to store paths not available in the target Nix store will fail.
>
> Use [`nix-store --query`](@docroot@/command-ref/nix-store/query.md) to obtain the closure of a store path.
This command is different from [`nix-store --dump`](./dump.md), which produces a [Nix archive](@docroot@/glossary.md#gloss-nar) that *does not* contain the set of [references](@docroot@/glossary.md#gloss-reference) of a given store path.
> **Note**
>
> For efficient transfer of closures to remote machines over SSH, use [`nix-copy-closure`](@docroot@/command-ref/nix-copy-closure.md).
[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Examples
> **Example**
>
> Deploy GNU Hello to an airgapped machine via USB stick.
>
> Write the closure to the block device on a machine with internet connection:
>
> ```shell-session
> [alice@itchy]$ storePath=$(nix-build '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello --no-out-link)
> [alice@itchy]$ nix-store --export $(nix-store --query --requisites $storePath) | sudo dd of=/dev/usb
> ```
>
> Read the closure from the block device on the machine without internet connection:
>
> ```shell-session
> [bob@scratchy]$ hello=$(sudo dd if=/dev/usb | nix-store --import | tail -1)
> [bob@scratchy]$ $hello/bin/hello
> Hello, world!
> ```

76
doc/manual/source/command-ref/nix-store/gc.md Normal file
View file

@ -0,0 +1,76 @@
# Name
`nix-store --gc` - run garbage collection
# Synopsis
`nix-store` `--gc` [`--print-roots` | `--print-live` | `--print-dead`] [`--max-freed` *bytes*]
# Description
Without additional flags, the operation `--gc` performs a garbage
collection on the Nix store. That is, all paths in the Nix store not
reachable via file system references from a set of “roots”, are deleted.
The following suboperations may be specified:
- `--print-roots`
This operation prints on standard output the set of roots used by
the garbage collector.
- `--print-live`
This operation prints on standard output the set of “live” store
paths, which are all the store paths reachable from the roots. Live
paths should never be deleted, since that would break consistency —
it would become possible that applications are installed that
reference things that are no longer present in the store.
- `--print-dead`
This operation prints out on standard output the set of “dead” store
paths, which is just the opposite of the set of live paths: any path
in the store that is not live (with respect to the roots) is dead.
By default, all unreachable paths are deleted. The following options
control what gets deleted and in what order:
- `--max-freed` *bytes*
Keep deleting paths until at least *bytes* bytes have been deleted,
then stop. The argument *bytes* can be followed by the
multiplicative suffix `K`, `M`, `G` or `T`, denoting KiB, MiB, GiB
or TiB units.
The behaviour of the collector is also influenced by the
`keep-outputs` and `keep-derivations` settings in the Nix
configuration file.
By default, the collector prints the total number of freed bytes when it
finishes (or when it is interrupted). With `--print-dead`, it prints the
number of bytes that would be freed.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Examples
To delete all unreachable paths, just do:
```console
$ nix-store --gc
deleting `/nix/store/kq82idx6g0nyzsp2s14gfsc38npai7lf-cairo-1.0.4.tar.gz.drv'
...
8825586 bytes freed (8.42 MiB)
```
To delete at least 100 MiBs of unreachable paths:
```console
$ nix-store --gc --max-freed $((100 * 1024 * 1024))
```

29
doc/manual/source/command-ref/nix-store/generate-binary-cache-key.md Normal file
View file

@ -0,0 +1,29 @@
# Name
`nix-store --generate-binary-cache-key` - generate key pair to use for a binary cache
## Synopsis
`nix-store` `--generate-binary-cache-key` *key-name* *secret-key-file* *public-key-file*
## Description
This command generates an [Ed25519 key pair](http://ed25519.cr.yp.to/)
that can be used to create a signed binary cache. It takes three
mandatory parameters:
1. A key name, such as `cache.example.org-1`, that is used to look up
keys on the client when it verifies signatures. It can be anything,
but it’s suggested to use the host name of your cache (e.g.
`cache.example.org`) with a suffix denoting the number of the key
(to be incremented every time you need to revoke a key).
2. The file name where the secret key is to be stored.
3. The file name where the public key is to be stored.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}

43
doc/manual/source/command-ref/nix-store/import.md Normal file
View file

@ -0,0 +1,43 @@
# Name
`nix-store --import` - import [Nix Archive] into the store
[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
# Synopsis
`nix-store` `--import`
# Description
The operation `--import` reads a serialisation of a set of [store objects](@docroot@/glossary.md#gloss-store-object) produced by [`nix-store --export`](./export.md) from standard input, and adds those store objects to the specified [Nix store](@docroot@/store/index.md).
Paths that already exist in the target Nix store are ignored.
If a path [refers](@docroot@/glossary.md#gloss-reference) to another path that doesn’t exist in the target Nix store, the import fails.
> **Note**
>
> For efficient transfer of closures to remote machines over SSH, use [`nix-copy-closure`](@docroot@/command-ref/nix-copy-closure.md).
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Examples
> **Example**
>
> Given a closure of GNU Hello as a file:
>
> ```shell-session
> $ storePath="$(nix-build '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello --no-out-link)"
> $ nix-store --export $(nix-store --query --requisites $storePath) > hello.closure
> ```
>
> Import the closure into a [remote SSH store](@docroot@/store/types/ssh-store.md) using the [`--store`](@docroot@/command-ref/conf-file.md#conf-store) option:
>
> ```console
> $ nix-store --import --store ssh://alice@itchy.example.org < hello.closure
> ```

18
doc/manual/source/command-ref/nix-store/load-db.md Normal file
View file

@ -0,0 +1,18 @@
# Name
`nix-store --load-db` - import Nix database
# Synopsis
`nix-store` `--load-db`
# Description
The operation `--load-db` reads a dump of the Nix database created by
`--dump-db` from standard input and loads it into the Nix database.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}

36
doc/manual/source/command-ref/nix-store/opt-common.md Normal file
View file

@ -0,0 +1,36 @@
# Options
The following options are allowed for all `nix-store` operations, but may not always have an effect.
- <span id="opt-add-root">[`--add-root`](#opt-add-root)</span> *path*
Causes the result of a realisation (`--realise` and
`--force-realise`) to be registered as a root of the garbage
collector. *path* will be created as a symlink to the resulting
store path. In addition, a uniquely named symlink to *path* will
be created in `/nix/var/nix/gcroots/auto/`. For instance,
```console
$ nix-store --add-root /home/eelco/bla/result --realise ...
$ ls -l /nix/var/nix/gcroots/auto
lrwxrwxrwx 1 ... 2005-03-13 21:10 dn54lcypm8f8... -> /home/eelco/bla/result
$ ls -l /home/eelco/bla/result
lrwxrwxrwx 1 ... 2005-03-13 21:10 /home/eelco/bla/result -> /nix/store/1r11343n6qd4...-f-spot-0.0.10
```
Thus, when `/home/eelco/bla/result` is removed, the GC root in the
`auto` directory becomes a dangling symlink and will be ignored by
the collector.
> **Warning**
>
> Note that it is not possible to move or rename GC roots, since
> the symlink in the `auto` directory will still point to the old
> location.
If there are multiple results, then multiple symlinks will be
created by sequentially numbering symlinks beyond the first one
(e.g., `foo`, `foo-2`, `foo-3`, and so on).

41
doc/manual/source/command-ref/nix-store/optimise.md Normal file
View file

@ -0,0 +1,41 @@
# Name
`nix-store --optimise` - reduce disk space usage
## Synopsis
`nix-store` `--optimise`
## Description
The operation `--optimise` reduces Nix store disk space usage by finding
identical files in the store and hard-linking them to each other. It
typically reduces the size of the store by something like 25-35%. Only
regular files and symlinks are hard-linked in this manner. Files are
considered identical when they have the same [Nix Archive (NAR)][Nix Archive] serialisation:
that is, regular files must have the same contents and permission
(executable or non-executable), and symlinks must have the same
contents.
After completion, or when the command is interrupted, a report on the
achieved savings is printed on standard error.
Use `-vv` or `-vvv` to get some progress indication.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
## Example
```console
$ nix-store --optimise
hashing files in `/nix/store/qhqx7l2f1kmwihc9bnxs7rc159hsxnf3-gcc-4.1.1'
...
541838819 bytes (516.74 MiB) freed by hard-linking 54143 files;
there are 114486 files with equal contents out of 215894 files in total
```
[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive

31
doc/manual/source/command-ref/nix-store/print-env.md Normal file
View file

@ -0,0 +1,31 @@
# Name
`nix-store --print-env` - print the build environment of a derivation
## Synopsis
`nix-store` `--print-env` *drvpath*
## Description
The operation `--print-env` prints out the environment of a derivation
in a format that can be evaluated by a shell. The command line arguments
of the builder are placed in the variable `_args`.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
## Example
```console
$ nix-store --print-env $(nix-instantiate '<nixpkgs>' -A firefox)
…
export src; src='/nix/store/plpj7qrwcz94z2psh6fchsi7s8yihc7k-firefox-12.0.source.tar.bz2'
export stdenv; stdenv='/nix/store/7c8asx3yfrg5dg1gzhzyq2236zfgibnn-stdenv'
export system; system='x86_64-linux'
export _args; _args='-e /nix/store/9krlzvny65gdc8s7kpb6lkx8cd02c25c-default-builder.sh'
```

243
doc/manual/source/command-ref/nix-store/query.md Normal file
View file

@ -0,0 +1,243 @@
# Name
`nix-store --query` - display information about store paths
# Synopsis
`nix-store` {`--query` | `-q`}
{`--outputs` | `--requisites` | `-R` | `--references` | `--referrers` |
`--referrers-closure` | `--deriver` | `-d` | `--valid-derivers` |
`--graph` | `--tree` | `--binding` *name* | `-b` *name* | `--hash` |
`--size` | `--roots`}
[`--use-output`] [`-u`] [`--force-realise`] [`-f`]
*paths…*
# Description
The operation `--query` displays various bits of information about the
store paths . The queries are described below. At most one query can be
specified. The default query is `--outputs`.
The paths *paths* may also be symlinks from outside of the Nix store, to
the Nix store. In that case, the query is applied to the target of the
symlink.
# Common query options
- `--use-output` / `-u`
For each argument to the query that is a [store derivation], apply the
query to the output path of the derivation instead.
- `--force-realise` / `-f`
Realise each argument to the query first (see [`nix-store --realise`](./realise.md)).
[store derivation]: @docroot@/glossary.md#gloss-store-derivation
# Queries
- `--outputs`
Prints out the [output paths] of the store
derivations *paths*. These are the paths that will be produced when
the derivation is built.
[output paths]: @docroot@/glossary.md#gloss-output-path
- `--requisites` / `-R`
Prints out the [closure] of the store path *paths*.
[closure]: @docroot@/glossary.md#gloss-closure
This query has one option:
- `--include-outputs`
Also include the existing output paths of [store derivation]s,
and their closures.
This query can be used to implement various kinds of deployment. A
*source deployment* is obtained by distributing the closure of a
store derivation. A *binary deployment* is obtained by distributing
the closure of an output path. A *cache deployment* (combined
source/binary deployment, including binaries of build-time-only
dependencies) is obtained by distributing the closure of a store
derivation and specifying the option `--include-outputs`.
- `--references`
Prints the set of [references] of the store paths
*paths*, that is, their immediate dependencies. (For *all*
dependencies, use `--requisites`.)
[references]: @docroot@/glossary.md#gloss-reference
- `--referrers`
Prints the set of *referrers* of the store paths *paths*, that is,
the store paths currently existing in the Nix store that refer to
one of *paths*. Note that contrary to the references, the set of
referrers is not constant; it can change as store paths are added or
removed.
- `--referrers-closure`
Prints the closure of the set of store paths *paths* under the
referrers relation; that is, all store paths that directly or
indirectly refer to one of *paths*. These are all the path currently
in the Nix store that are dependent on *paths*.
- `--deriver` / `-d`
Prints the [deriver] that was used to build the store paths *paths*. If
the path has no deriver (e.g., if it is a source file), or if the
deriver is not known (e.g., in the case of a binary-only
deployment), the string `unknown-deriver` is printed.
The returned deriver is not guaranteed to exist in the local store, for
example when *paths* were substituted from a binary cache.
Use `--valid-derivers` instead to obtain valid paths only.
[deriver]: @docroot@/glossary.md#gloss-deriver
- `--valid-derivers`
Prints a set of derivation files (`.drv`) which are supposed produce
said paths when realized. Might print nothing, for example for source paths
or paths substituted from a binary cache.
- `--graph`
Prints the references graph of the store paths *paths* in the format
of the `dot` tool of AT\&T's [Graphviz
package](http://www.graphviz.org/). This can be used to visualise
dependency graphs. To obtain a build-time dependency graph, apply
this to a store derivation. To obtain a runtime dependency graph,
apply it to an output path.
- `--tree`
Prints the references graph of the store paths *paths* as a nested
ASCII tree. References are ordered by descending closure size; this
tends to flatten the tree, making it more readable. The query only
recurses into a store path when it is first encountered; this
prevents a blowup of the tree representation of the graph.
- `--graphml`
Prints the references graph of the store paths *paths* in the
[GraphML](http://graphml.graphdrawing.org/) file format. This can be
used to visualise dependency graphs. To obtain a build-time
dependency graph, apply this to a [store derivation]. To obtain a
runtime dependency graph, apply it to an output path.
- `--binding` *name* / `-b` *name*
Prints the value of the attribute *name* (i.e., environment
variable) of the [store derivation]s *paths*. It is an error for a
derivation to not have the specified attribute.
- `--hash`
Prints the SHA-256 hash of the contents of the store paths *paths*
(that is, the hash of the output of `nix-store --dump` on the given
paths). Since the hash is stored in the Nix database, this is a fast
operation.
- `--size`
Prints the size in bytes of the contents of the store paths *paths*
— to be precise, the size of the output of `nix-store --dump` on
the given paths. Note that the actual disk space required by the
store paths may be higher, especially on filesystems with large
cluster sizes.
- `--roots`
Prints the garbage collector roots that point, directly or
indirectly, at the store paths *paths*.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Examples
Print the closure (runtime dependencies) of the `svn` program in the
current user environment:
```console
$ nix-store --query --requisites $(which svn)
/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
/nix/store/9lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4
...
```
Print the build-time dependencies of `svn`:
```console
$ nix-store --query --requisites $(nix-store --query --deriver $(which svn))
/nix/store/02iizgn86m42q905rddvg4ja975bk2i4-grep-2.5.1.tar.bz2.drv
/nix/store/07a2bzxmzwz5hp58nf03pahrv2ygwgs3-gcc-wrapper.sh
/nix/store/0ma7c9wsbaxahwwl04gbw3fcd806ski4-glibc-2.3.4.drv
... lots of other paths ...
```
The difference with the previous example is that we ask the closure of
the derivation (`-qd`), not the closure of the output path that contains
`svn`.
Show the build-time dependencies as a tree:
```console
$ nix-store --query --tree $(nix-store --query --deriver $(which svn))
/nix/store/7i5082kfb6yjbqdbiwdhhza0am2xvh6c-subversion-1.1.4.drv
+---/nix/store/d8afh10z72n8l1cr5w42366abiblgn54-builder.sh
+---/nix/store/fmzxmpjx2lh849ph0l36snfj9zdibw67-bash-3.0.drv
| +---/nix/store/570hmhmx3v57605cqg9yfvvyh0nnb8k8-bash
| +---/nix/store/p3srsbd8dx44v2pg6nbnszab5mcwx03v-builder.sh
...
```
Show all paths that depend on the same OpenSSL library as `svn`:
```console
$ nix-store --query --referrers $(nix-store --query --binding openssl $(nix-store --query --deriver $(which svn)))
/nix/store/23ny9l9wixx21632y2wi4p585qhva1q8-sylpheed-1.0.0
/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
/nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3
/nix/store/l51240xqsgg8a7yrbqdx1rfzyv6l26fx-lynx-2.8.5
```
Show all paths that directly or indirectly depend on the Glibc (C
library) used by `svn`:
```console
$ nix-store --query --referrers-closure $(ldd $(which svn) | grep /libc.so | awk '{print $3}')
/nix/store/034a6h4vpz9kds5r6kzb9lhh81mscw43-libgnomeprintui-2.8.2
/nix/store/15l3yi0d45prm7a82pcrknxdh6nzmxza-gawk-3.1.4
...
```
Note that `ldd` is a command that prints out the dynamic libraries used
by an ELF executable.
Make a picture of the runtime dependency graph of the current user
environment:
```console
$ nix-store --query --graph ~/.nix-profile | dot -Tps > graph.ps
$ gv graph.ps
```
Show every garbage collector root that points to a store path that
depends on `svn`:
```console
$ nix-store --query --roots $(which svn)
/nix/var/nix/profiles/default-81-link
/nix/var/nix/profiles/default-82-link
/home/eelco/.local/state/nix/profiles/profile-97-link
```

38
doc/manual/source/command-ref/nix-store/read-log.md Normal file
View file

@ -0,0 +1,38 @@
# Name
`nix-store --read-log` - print build log
# Synopsis
`nix-store` {`--read-log` | `-l`} *paths…*
# Description
The operation `--read-log` prints the build log of the specified store
paths on standard output. The build log is whatever the builder of a
derivation wrote to standard output and standard error. If a store path
is not a derivation, the deriver of the store path is used.
Build logs are kept in `/nix/var/log/nix/drvs`. However, there is no
guarantee that a build log is available for any particular store path.
For instance, if the path was downloaded as a pre-built binary through a
substitute, then the log is unavailable.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Example
```console
$ nix-store --read-log $(which ktorrent)
building /nix/store/dhc73pvzpnzxhdgpimsd9sw39di66ph1-ktorrent-2.2.1
unpacking sources
unpacking source archive /nix/store/p8n1jpqs27mgkjw07pb5269717nzf5f8-ktorrent-2.2.1.tar.gz
ktorrent-2.2.1/
ktorrent-2.2.1/NEWS
...
```

94
doc/manual/source/command-ref/nix-store/realise.md Normal file
View file

@ -0,0 +1,94 @@
# Name
`nix-store --realise` - build or fetch store objects
# Synopsis
`nix-store` {`--realise` | `-r`} *paths…* [`--dry-run`]
# Description
Each of *paths* is processed as follows:
- If the path leads to a [store derivation]:
1. If it is not [valid], substitute the store derivation file itself.
2. Realise its [output paths]:
- Try to fetch from [substituters] the [store objects] associated with the output paths in the store derivation's [closure].
- With [content-addressed derivations] (experimental):
Determine the output paths to realise by querying content-addressed realisation entries in the [Nix database].
- For any store paths that cannot be substituted, produce the required store objects:
1. Realise all outputs of the derivation's dependencies
2. Run the derivation's [`builder`](@docroot@/language/derivations.md#attr-builder) executable
<!-- TODO: Link to build process page #8888 -->
- Otherwise, and if the path is not already valid: Try to fetch the associated [store objects] in the path's [closure] from [substituters].
If no substitutes are available and no store derivation is given, realisation fails.
[store paths]: @docroot@/store/store-path.md
[valid]: @docroot@/glossary.md#gloss-validity
[store derivation]: @docroot@/glossary.md#gloss-store-derivation
[output paths]: @docroot@/glossary.md#gloss-output-path
[store objects]: @docroot@/store/store-object.md
[closure]: @docroot@/glossary.md#gloss-closure
[substituters]: @docroot@/command-ref/conf-file.md#conf-substituters
[content-addressed derivations]: @docroot@/development/experimental-features.md#xp-feature-ca-derivations
[Nix database]: @docroot@/glossary.md#gloss-nix-database
The resulting paths are printed on standard output.
For non-derivation arguments, the argument itself is printed.
{{#include ../status-build-failure.md}}
# Options
- `--dry-run`
Print on standard error a description of what packages would be
built or downloaded, without actually performing the operation.
- `--ignore-unknown`
If a non-derivation path does not have a substitute, then silently
ignore it.
- `--check`
This option allows you to check whether a derivation is
deterministic. It rebuilds the specified derivation and checks
whether the result is bitwise-identical with the existing outputs,
printing an error if that’s not the case. The outputs of the
specified derivation must already exist. When used with `-K`, if an
output path is not identical to the corresponding output from the
previous build, the new output path is left in
`/nix/store/name.check.`
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Examples
This operation is typically used to build [store derivation]s produced by
[`nix-instantiate`](@docroot@/command-ref/nix-instantiate.md):
```console
$ nix-store --realise $(nix-instantiate ./test.nix)
/nix/store/31axcgrlbfsxzmfff1gyj1bf62hvkby2-aterm-2.3.1
```
This is essentially what [`nix-build`](@docroot@/command-ref/nix-build.md) does.
To test whether a previously-built derivation is deterministic:
```console
$ nix-build '<nixpkgs>' --attr hello --check -K
```
Use [`nix-store --read-log`](./read-log.md) to show the stderr and stdout of a build:
```console
$ nix-store --read-log $(nix-instantiate ./test.nix)
```

35
doc/manual/source/command-ref/nix-store/repair-path.md Normal file
View file

@ -0,0 +1,35 @@
# Name
`nix --repair-path` - re-download path from substituter
# Synopsis
`nix-store` `--repair-path` *paths…*
# Description
The operation `--repair-path` attempts to “repair” the specified paths
by redownloading them using the available substituters. If no
substitutes are available, then repair is not possible.
> **Warning**
>
> During repair, there is a very small time window during which the old
> path (if it exists) is moved out of the way and replaced with the new
> path. If repair is interrupted in between, then the system may be left
> in a broken state (e.g., if the path contains a critical system
> component like the GNU C Library).
# Example
```console
$ nix-store --verify-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
path `/nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13' was modified!
expected hash `2db57715ae90b7e31ff1f2ecb8c12ec1cc43da920efcbe3b22763f36a1861588',
got `481c5aa5483ebc97c20457bb8bca24deea56550d3985cda0027f67fe54b808e4'
$ nix-store --repair-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
fetching path `/nix/store/d7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13'...
…
```

20
doc/manual/source/command-ref/nix-store/restore.md Normal file
View file

@ -0,0 +1,20 @@
# Name
`nix-store --restore` - extract a Nix archive
## Synopsis
`nix-store` `--restore` *path*
## Description
The operation `--restore` unpacks a [Nix Archive (NAR)][Nix Archive] to *path*, which must
not already exist. The archive is read from standard input.
[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}

39
doc/manual/source/command-ref/nix-store/serve.md Normal file
View file

@ -0,0 +1,39 @@
# Name
`nix-store --serve` - serve local Nix store over SSH
# Synopsis
`nix-store` `--serve` [`--write`]
# Description
The operation `--serve` provides access to the Nix store over stdin and
stdout, and is intended to be used as a means of providing Nix store
access to a restricted ssh user.
The following flags are available:
- `--write`
Allow the connected client to request the realization of
derivations. In effect, this can be used to make the host act as a
remote builder.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
# Examples
To turn a host into a build server, the `authorized_keys` file can be
used to provide build access to a given SSH public key:
```console
$ cat <<EOF >>/root/.ssh/authorized_keys
command="nice -n20 nix-store --serve --write" ssh-rsa AAAAB3NzaC1yc2EAAAA...
EOF
```

29
doc/manual/source/command-ref/nix-store/verify-path.md Normal file
View file

@ -0,0 +1,29 @@
# Name
`nix-store --verify-path` - check path contents against Nix database
## Synopsis
`nix-store` `--verify-path` *paths…*
## Description
The operation `--verify-path` compares the contents of the given store
paths to their cryptographic hashes stored in Nix’s database. For every
changed path, it prints a warning message. The exit status is 0 if no
path has changed, and 1 otherwise.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}
## Example
To verify the integrity of the `svn` command and all its dependencies:
```console
$ nix-store --verify-path $(nix-store --query --requisites $(which svn))
```

38
doc/manual/source/command-ref/nix-store/verify.md Normal file
View file

@ -0,0 +1,38 @@
# Name
`nix-store --verify` - check Nix database for consistency
# Synopsis
`nix-store` `--verify` [`--check-contents`] [`--repair`]
# Description
The operation `--verify` verifies the internal consistency of the Nix
database, and the consistency between the Nix database and the Nix
store. Any inconsistencies encountered are automatically repaired.
Inconsistencies are generally the result of the Nix store or database
being modified by non-Nix tools, or of bugs in Nix itself.
This operation has the following options:
- `--check-contents`
Checks that the contents of every valid store path has not been
altered by computing a SHA-256 hash of the contents and comparing it
with the hash stored in the Nix database at build time. Paths that
have been modified are printed out. For large stores,
`--check-contents` is obviously quite slow.
- `--repair`
If any valid path is missing from the store, or (if
`--check-contents` is given) the contents of a valid path has been
modified, then try to repair the path by redownloading it. See
`nix-store --repair-path` for details.
{{#include ./opt-common.md}}
{{#include ../opt-common.md}}
{{#include ../env-common.md}}

230
doc/manual/source/command-ref/opt-common.md Normal file
View file

@ -0,0 +1,230 @@
<!-- Some of the options documented here are hardcopied from
src/libcmd/common-eval-args.cc
-->
# Common Options
Most Nix commands accept the following command-line options:
- <span id="opt-help">[`--help`](#opt-help)</span>
Prints out a summary of the command syntax and exits.
- <span id="opt-version">[`--version`](#opt-version)</span>
Prints out the Nix version number on standard output and exits.
- <span id="opt-verbose">[`--verbose`](#opt-verbose)</span> / `-v`
Increases the level of verbosity of diagnostic messages printed on standard error.
For each Nix operation, the information printed on standard output is well-defined;
any diagnostic information is printed on standard error, never on standard output.
This option may be specified repeatedly.
Currently, the following verbosity levels exist:
- `0` “Errors only”
Only print messages explaining why the Nix invocation failed.
- `1` “Informational”
Print *useful* messages about what Nix is doing.
This is the default.
- `2` “Talkative”
Print more informational messages.
- `3` “Chatty”
Print even more informational messages.
- `4` “Debug”
Print debug information.
- `5` “Vomit”
Print vast amounts of debug information.
- <span id="opt-quiet">[`--quiet`](#opt-quiet)</span>
Decreases the level of verbosity of diagnostic messages printed on standard error.
This is the inverse option to `-v` / `--verbose`.
This option may be specified repeatedly.
See the previous verbosity levels list.
- <span id="opt-log-format">[`--log-format`](#opt-log-format)</span> *format*
This option can be used to change the output of the log format, with *format* being one of:
- `raw`
This is the raw format, as outputted by nix-build.
- `internal-json`
Outputs the logs in a structured manner.
> **Warning**
>
> While the schema itself is relatively stable, the format of
> the error-messages (namely of the `msg`-field) can change
> between releases.
- `bar`
Only display a progress bar during the builds.
- `bar-with-logs`
Display the raw logs, with the progress bar at the bottom.
- <span id="opt-no-build-output">[`--no-build-output`](#opt-no-build-output)</span> / `-Q`
By default, output written by builders to standard output and standard error is echoed to the Nix command's standard error.
This option suppresses this behaviour.
Note that the builder's standard output and error are always written to a log file in `prefix/nix/var/log/nix`.
- <span id="opt-max-jobs">[`--max-jobs`](#opt-max-jobs)</span> / `-j` *number*
Sets the maximum number of build jobs that Nix will perform in parallel to the specified number.
Specify `auto` to use the number of CPUs in the system.
The default is specified by the `max-jobs` configuration setting, which itself defaults to `1`.
A higher value is useful on SMP systems or to exploit I/O latency.
Setting it to `0` disallows building on the local machine, which is useful when you want builds to happen only on remote builders.
- <span id="opt-cores">[`--cores`](#opt-cores)</span>
Sets the value of the `NIX_BUILD_CORES` environment variable in the invocation of builders.
Builders can use this variable at their discretion to control the maximum amount of parallelism.
For instance, in Nixpkgs, if the derivation attribute `enableParallelBuilding` is set to `true`, the builder passes the `-jN` flag to GNU Make.
It defaults to the value of the `cores` configuration setting, if set, or `1` otherwise.
The value `0` means that the builder should use all available CPU cores in the system.
- <span id="opt-max-silent-time">[`--max-silent-time`](#opt-max-silent-time)</span>
Sets the maximum number of seconds that a builder can go without producing any data on standard output or standard error.
The default is specified by the `max-silent-time` configuration setting.
`0` means no time-out.
- <span id="opt-timeout">[`--timeout`](#opt-timeout)</span>
Sets the maximum number of seconds that a builder can run.
The default is specified by the `timeout` configuration setting.
`0` means no timeout.
- <span id="opt-keep-going">[`--keep-going`](#opt-keep-going)</span> / `-k`
Keep going in case of failed builds, to the greatest extent possible.
That is, if building an input of some derivation fails, Nix will still build the other inputs, but not the derivation itself.
Without this option, Nix stops if any build fails (except for builds of substitutes), possibly killing builds in progress (in case of parallel or distributed builds).
- <span id="opt-keep-failed">[`--keep-failed`](#opt-keep-failed)</span> / `-K`
Specifies that in case of a build failure, the temporary directory (usually in `/tmp`) in which the build takes place should not be deleted.
The path of the build directory is printed as an informational message.
- <span id="opt-fallback">[`--fallback`](#opt-fallback)</span>
Whenever Nix attempts to build a derivation for which substitutes are known for each output path, but realising the output paths through the substitutes fails, fall back on building the derivation.
The most common scenario in which this is useful is when we have registered substitutes in order to perform binary distribution from, say, a network repository.
If the repository is down, the realisation of the derivation will fail.
When this option is specified, Nix will build the derivation instead.
Thus, installation from binaries falls back on installation from source.
This option is not the default since it is generally not desirable for a transient failure in obtaining the substitutes to lead to a full build from source (with the related consumption of resources).
- <span id="opt-readonly-mode">[`--readonly-mode`](#opt-readonly-mode)</span>
When this option is used, no attempt is made to open the Nix database.
Most Nix operations do need database access, so those operations will fail.
- <span id="opt-arg">[`--arg`](#opt-arg)</span> *name* *value*
This option is accepted by `nix-env`, `nix-instantiate`, `nix-shell` and `nix-build`.
When evaluating Nix expressions, the expression evaluator will automatically try to call functions that it encounters.
It can automatically call functions for which every argument has a [default value](@docroot@/language/syntax.md#functions) (e.g., `{ argName ? defaultValue }: ...`).
With `--arg`, you can also call functions that have arguments without a default value (or override a default value).
That is, if the evaluator encounters a function with an argument named *name*, it will call it with value *value*.
For instance, the top-level `default.nix` in Nixpkgs is actually a function:
```nix
{ # The system (e.g., `i686-linux') for which to build the packages.
system ? builtins.currentSystem
...
}: ...
```
So if you call this Nix expression (e.g., when you do `nix-env --install --attr pkgname`), the function will be called automatically using the value [`builtins.currentSystem`](@docroot@/language/builtins.md) for the `system` argument.
You can override this using `--arg`, e.g., `nix-env --install --attr pkgname --arg system \"i686-freebsd\"`.
(Note that since the argument is a Nix string literal, you have to escape the quotes.)
- <span id="opt-arg-from-file">[`--arg-from-file`](#opt-arg-from-file)</span> *name* *path*
Pass the contents of file *path* as the argument *name* to Nix functions.
- <span id="opt-arg-from-stdin">[`--arg-from-stdin`](#opt-arg-from-stdin)</span> *name*
Pass the contents of stdin as the argument *name* to Nix functions.
- <span id="opt-argstr">[`--argstr`](#opt-argstr)</span> *name* *value*
This option is like `--arg`, only the value is not a Nix expression but a string.
So instead of `--arg system \"i686-linux\"` (the outer quotes are to keep the shell happy) you can say `--argstr system i686-linux`.
- <span id="opt-attr">[`--attr`](#opt-attr)</span> / `-A` *attrPath*
Select an attribute from the top-level Nix expression being evaluated.
(`nix-env`, `nix-instantiate`, `nix-build` and `nix-shell` only.)
The *attribute path* *attrPath* is a sequence of attribute names separated by dots.
For instance, given a top-level Nix expression *e*, the attribute path `xorg.xorgserver` would cause the expression `e.xorg.xorgserver` to be used.
See [`nix-env --install`](@docroot@/command-ref/nix-env/install.md) for some concrete examples.
In addition to attribute names, you can also specify array indices.
For instance, the attribute path `foo.3.bar` selects the `bar`
attribute of the fourth element of the array in the `foo` attribute
of the top-level expression.
- <span id="opt-eval-store">[`--eval-store`](#opt-eval-store)</span> *store-url*
The [URL to the Nix store](@docroot@/store/types/index.md#store-url-format) to use for evaluation, i.e. where to store derivations (`.drv` files) and inputs referenced by them.
- <span id="opt-expr">[`--expr`](#opt-expr)</span> / `-E`
Interpret the command line arguments as a list of Nix expressions to be parsed and evaluated, rather than as a list of file names of Nix expressions.
(`nix-instantiate`, `nix-build` and `nix-shell` only.)
For `nix-shell`, this option is commonly used to give you a shell in which you can build the packages returned by the expression.
If you want to get a shell which contain the *built* packages ready for use, give your expression to the `nix-shell --packages ` convenience flag instead.
- <span id="opt-I">[`-I` / `--include`](#opt-I)</span> *path*
Add an entry to the list of search paths used to resolve [lookup paths](@docroot@/language/constructs/lookup-path.md).
This option may be given multiple times.
Paths added through `-I` take precedence over the [`nix-path` configuration setting](@docroot@/command-ref/conf-file.md#conf-nix-path) and the [`NIX_PATH` environment variable](@docroot@/command-ref/env-common.md#env-NIX_PATH).
- <span id="opt-impure">[`--impure`](#opt-impure)</span>
Allow access to mutable paths and repositories.
- <span id="opt-option">[`--option`](#opt-option)</span> *name* *value*
Set the Nix configuration option *name* to *value*.
This overrides settings in the Nix configuration file (see nix.conf5).
- <span id="opt-repair">[`--repair`](#opt-repair)</span>
Fix corrupted or missing store paths by redownloading or rebuilding them.
Note that this is slow because it requires computing a cryptographic hash of the contents of every path in the closure of the build.
Also note the warning under `nix-store --repair-path`.
> **Note**
>
> See [`man nix.conf`](@docroot@/command-ref/conf-file.md#command-line-flags) for overriding configuration settings with command line flags.

34
doc/manual/source/command-ref/status-build-failure.md Normal file
View file

@ -0,0 +1,34 @@
# Special exit codes for build failure
1xx status codes are used when requested builds failed.
The following codes are in use:
- `100` Generic build failure
The builder process returned with a non-zero exit code.
- `101` Build timeout
The build was aborted because it did not complete within the specified `timeout`.
- `102` Hash mismatch
The build output was rejected because it does not match the
[`outputHash` attribute of the derivation](@docroot@/language/advanced-attributes.md).
- `104` Not deterministic
The build succeeded in check mode but the resulting output is not binary reproducible.
With the `--keep-going` flag it's possible for multiple failures to occur.
In this case the 1xx status codes are or combined using
[bitwise OR](https://en.wikipedia.org/wiki/Bitwise_operation#OR).
```
0b1100100
^^^^
|||`- timeout
||`-- output hash mismatch
|`--- build failure
`---- not deterministic
```

3
doc/manual/source/command-ref/utilities.md Normal file
View file

@ -0,0 +1,3 @@
# Utilities
This section lists utilities that you can use when you work with Nix.

211
doc/manual/source/development/building.md Normal file
View file

@ -0,0 +1,211 @@
# Building Nix
To build all dependencies and start a shell in which all environment variables are set up so that those dependencies can be found:
```console
$ nix develop
```
This shell also adds `./outputs/bin/nix` to your `$PATH` so you can run `nix` immediately after building it.
To get a shell with one of the other [supported compilation environments](#compilation-environments):
```console
$ nix develop .#native-clangStdenvPackages
```
> **Note**
>
> Use `ccacheStdenv` to drastically improve rebuild time.
> By default, [ccache](https://ccache.dev) keeps artifacts in `~/.cache/ccache/`.
To build Nix itself in this shell:
```console
[nix-shell]$ configurePhase
[nix-shell]$ buildPhase
```
To test it:
```console
[nix-shell]$ checkPhase
```
To install it in `$(pwd)/outputs`:
```console
[nix-shell]$ installPhase
[nix-shell]$ nix --version
nix (Nix) 2.12
```
For more information on running and filtering tests, see
[`testing.md`](./testing.md).
To build a release version of Nix for the current operating system and CPU architecture:
```console
$ nix build
```
You can also build Nix for one of the [supported platforms](#platforms).
## Platforms
Nix can be built for various platforms, as specified in [`flake.nix`]:
[`flake.nix`]: https://github.com/nixos/nix/blob/master/flake.nix
- `x86_64-linux`
- `x86_64-darwin`
- `i686-linux`
- `aarch64-linux`
- `aarch64-darwin`
- `armv6l-linux`
- `armv7l-linux`
- `riscv64-linux`
In order to build Nix for a different platform than the one you're currently
on, you need a way for your current Nix installation to build code for that
platform. Common solutions include [remote build machines] and [binary format emulation]
(only supported on NixOS).
[remote builders]: @docroot@/language/derivations.md#attr-builder
[binary format emulation]: https://nixos.org/manual/nixos/stable/options.html#opt-boot.binfmt.emulatedSystems
Given such a setup, executing the build only requires selecting the respective attribute.
For example, to compile for `aarch64-linux`:
```console
$ nix build .#packages.aarch64-linux.default
```
Cross-compiled builds are available for:
- `armv6l-linux`
- `armv7l-linux`
- `riscv64-linux`
Add more [system types](#system-type) to `crossSystems` in `flake.nix` to bootstrap Nix on unsupported platforms.
### Building for multiple platforms at once
It is useful to perform multiple cross and native builds on the same source tree,
for example to ensure that better support for one platform doesn't break the build for another.
Meson thankfully makes this very easy by confining all build products to the build directory --- one simple shares the source directory between multiple build directories, each of which contains the build for Nix to a different platform.
Nixpkgs's `configurePhase` always chooses `build` in the current directory as the name and location of the build.
This makes having multiple build directories slightly more inconvenient.
The good news is that Meson/Ninja seem to cope well with relocating the build directory after it is created.
Here's how to do that
1. Configure as usual
```bash
configurePhase
```
2. Rename the build directory
```bash
cd .. # since `configurePhase` cd'd inside
mv build build-linux # or whatever name we want
cd build-linux
```
3. Build as usual
```bash
buildPhase
```
> **N.B.**
> [`nixpkgs#335818`](https://github.com/NixOS/nixpkgs/issues/335818) tracks giving `mesonConfigurePhase` proper support for custom build directories.
> When it is fixed, we can simplify these instructions and then remove this notice.
## System type
Nix uses a string with the following format to identify the *system type* or *platform* it runs on:
```
<cpu>-<os>[-<abi>]
```
It is set when Nix is compiled for the given system, and based on the output of [`config.guess`](https://github.com/nixos/nix/blob/master/config/config.guess) ([upstream](https://git.savannah.gnu.org/cgit/config.git/tree/config.guess)):
```
<cpu>-<vendor>-<os>[<version>][-<abi>]
```
When Nix is built such that `./configure` is passed any of the `--host`, `--build`, `--target` options, the value is based on the output of [`config.sub`](https://github.com/nixos/nix/blob/master/config/config.sub) ([upstream](https://git.savannah.gnu.org/cgit/config.git/tree/config.sub)):
```
<cpu>-<vendor>[-<kernel>]-<os>
```
For historic reasons and backward-compatibility, some CPU and OS identifiers are translated from the GNU Autotools naming convention in [`configure.ac`](https://github.com/nixos/nix/blob/master/configure.ac) as follows:
| `config.guess` | Nix |
|----------------------------|---------------------|
| `amd64` | `x86_64` |
| `i*86` | `i686` |
| `arm6` | `arm6l` |
| `arm7` | `arm7l` |
| `linux-gnu*` | `linux` |
| `linux-musl*` | `linux` |
## Compilation environments
Nix can be compiled using multiple environments:
- `stdenv`: default;
- `gccStdenv`: force the use of `gcc` compiler;
- `clangStdenv`: force the use of `clang` compiler;
- `ccacheStdenv`: enable [ccache], a compiler cache to speed up compilation.
To build with one of those environments, you can use
```console
$ nix build .#nix-ccacheStdenv
```
You can use any of the other supported environments in place of `nix-ccacheStdenv`.
## Editor integration
The `clangd` LSP server is installed by default on the `clang`-based `devShell`s.
See [supported compilation environments](#compilation-environments) and instructions how to [set up a shell with flakes](#nix-with-flakes).
To use the LSP with your editor, you will want a `compile_commands.json` file telling `clangd` how we are compiling the code.
Meson's configure always produces this inside the build directory.
Configure your editor to use the `clangd` from the `.#native-clangStdenvPackages` shell. You can do that either by running it inside the development shell, or by using [nix-direnv](https://github.com/nix-community/nix-direnv) and [the appropriate editor plugin](https://github.com/direnv/direnv/wiki#editor-integration).
> **Note**
>
> For some editors (e.g. Visual Studio Code), you may need to install a [special extension](https://open-vsx.org/extension/llvm-vs-code-extensions/vscode-clangd) for the editor to interact with `clangd`.
> Some other editors (e.g. Emacs, Vim) need a plugin to support LSP servers in general (e.g. [lsp-mode](https://github.com/emacs-lsp/lsp-mode) for Emacs and [vim-lsp](https://github.com/prabirshrestha/vim-lsp) for vim).
> Editor-specific setup is typically opinionated, so we will not cover it here in more detail.
## Formatting and pre-commit hooks
You may run the formatters as a one-off using:
```console
./maintainers/format.sh
```
If you'd like to run the formatters before every commit, install the hooks:
```
pre-commit-hooks-install
```
This installs [pre-commit](https://pre-commit.com) using [cachix/git-hooks.nix](https://github.com/cachix/git-hooks.nix).
When making a commit, pay attention to the console output.
If it fails, run `git add --patch` to approve the suggestions _and commit again_.
To refresh pre-commit hook's config file, do the following:
1. Exit the development shell and start it again by running `nix develop`.
2. If you also use the pre-commit hook, also run `pre-commit-hooks-install` again.

589
doc/manual/source/development/cli-guideline.md Normal file
View file

@ -0,0 +1,589 @@
# CLI guideline
## Goals
Purpose of this document is to provide a clear direction to **help design
delightful command line** experience. This document contains guidelines to
follow to ensure a consistent and approachable user experience.
## Overview
`nix` command provides a single entry to a number of sub-commands that help
**developers and system administrators** in the life-cycle of a software
project. We particularly need to pay special attention to help and assist new
users of Nix.
# Naming the `COMMANDS`
Words matter. Naming is an important part of the usability. Users will be
interacting with Nix on a regular basis so we should **name things for ease of
understanding**.
We recommend following the [Principle of Least
Astonishment](https://en.wikipedia.org/wiki/Principle_of_least_astonishment).
This means that you should **never use acronyms or abbreviations** unless they
are commonly used in other tools (e.g. `nix init`). And if the command name is
too long (> 10-12 characters) then shortening it makes sense (e.g.
“prioritization” → “priority”).
Commands should **follow a noun-verb dialogue**. Although noun-verb formatting
seems backwards from a speaking perspective (i.e. `nix store copy` vs. `nix
copy store`) it allows us to organize commands the same way users think about
completing an action (the group first, then the command).
## Naming rules
Rules are there to guide you by limiting your options. But not everything can
fit the rules all the time. In those cases document the exceptions in [Appendix
1: Commands naming exceptions](#appendix-1-commands-naming-exceptions) and
provide reason. The rules want to force a Nix developer to look, not just at
the command at hand, but also the command in a full context alongside other
`nix` commands.
```shell
$ nix [<GROUP>] <COMMAND> [<ARGUMENTS>] [<OPTIONS>]
```
- `GROUP`, `COMMAND`, `ARGUMENTS` and `OPTIONS` should be lowercase and in a
singular form.
- `GROUP` should be a **NOUN**.
- `COMMAND` should be a **VERB**.
- `ARGUMENTS` and `OPTIONS` are discussed in [*Input* section](#input).
## Classification
Some commands are more important, some less. While we want all of our commands
to be perfect we can only spend limited amount of time testing and improving
them.
This classification tries to separate commands in 3 categories in terms of
their importance in regards to the new users. Users who are likely to be
impacted the most by bad user experience.
- **Main commands**
Commands used for our main use cases and most likely used by new users. We
expect attention to details, such as:
- Proper use of [colors](#colors), [emojis](#special-unicode-characters)
and [aligning of text](#text-alignment).
- [Autocomplete](#shell-completion) of options.
- Show [next possible steps](#next-steps).
- Showing some [“tips”](#educate-the-user) when running logs running tasks
(eg. building / downloading) in order to teach users interesting bits of
Nix ecosystem.
- [Help pages](#help-is-essential) to be as good as we can write them
pointing to external documentation and tutorials for more.
Examples of such commands: `nix init`, `nix develop`, `nix build`, `nix run`,
...
- **Infrequently used commands**
From infrequently used commands we expect less attention to details, but
still some:
- Proper use of [colors](#colors), [emojis](#special-unicode-characters)
and [aligning of text](#text-alignment).
- [Autocomplete](#shell-completion) of options.
Examples of such commands: `nix edit`, `nix eval`, ...
- **Utility and scripting commands**
Commands that expose certain internal functionality of `nix`, mostly used by
other scripts.
- [Autocomplete](#shell-completion) of options.
Examples of such commands: `nix store copy`, `nix hash base16`, `nix store
ping`, ...
# Help is essential
Help should be built into your command line so that new users can gradually
discover new features when they need them.
## Looking for help
Since there is no standard way how user will look for help we rely on ways help
is provided by commonly used tools. As a guide for this we took `git` and
whenever in doubt look at it as a preferred direction.
The rules are:
- Help is shown by using `--help` or `help` command (eg `nix` `--``help` or
`nix help`).
- For non-COMMANDs (eg. `nix` `--``help` and `nix store` `--``help`) we **show
a summary** of most common use cases. Summary is presented on the STDOUT
without any use of PAGER.
- For COMMANDs (eg. `nix init` `--``help` or `nix help init`) we display the
man page of that command. By default the PAGER is used (as in `git`).
- At the end of either summary or man page there should be an URL pointing to
an online version of more detailed documentation.
- The structure of summaries and man pages should be the same as in `git`.
## Anticipate where help is needed
Even better then requiring the user to search for help is to anticipate and
predict when user might need it. Either because the lack of discoverability,
typo in the input or simply taking the opportunity to teach the user of
interesting - but less visible - details.
### Shell completion
This type of help is most common and almost expected by users. We need to
**provide the best shell completion** for `bash`, `zsh` and `fish`.
Completion needs to be **context aware**, this mean when a user types:
```shell
$ nix build n<TAB>
```
we need to display a list of flakes starting with `n`.
### Wrong input
As we all know we humans make mistakes, all the time. When a typo - intentional
or unintentional - is made, we should prompt for closest possible options or
point to the documentation which would educate user to not make the same
errors. Here are few examples:
In first example we prompt the user for typing wrong command name:
```shell
$ nix int
------------------------------------------------------------------------
Error! Command `int` not found.
------------------------------------------------------------------------
Did you mean:
|> nix init
|> nix input
```
Sometimes users will make mistake either because of a typo or simply because of
lack of discoverability. Our handling of this cases needs to be context
sensitive.
```shell
$ nix init --template=template#pyton
------------------------------------------------------------------------
Error! Template `template#pyton` not found.
------------------------------------------------------------------------
Initializing Nix project at `/path/to/here`.
Select a template for you new project:
|> template#python
template#python-pip
template#python-poetry
```
### Next steps
It can be invaluable to newcomers to show what a possible next steps and what
is the usual development workflow with Nix. For example:
```shell
$ nix init --template=template#python
Initializing project `template#python`
in `/home/USER/dev/new-project`
Next steps
|> nix develop -- to enter development environment
|> nix build -- to build your project
```
### Educate the user
We should take any opportunity to **educate users**, but at the same time we
must **be very very careful to not annoy users**. There is a thin line between
being helpful and being annoying.
An example of educating users might be to provide *Tips* in places where they
are waiting.
```shell
$ nix build
Started building my-project 1.2.3
Downloaded python3.8-poetry 1.2.3 in 5.3 seconds
Downloaded python3.8-requests 1.2.3 in 5.3 seconds
------------------------------------------------------------------------
Press `v` to increase logs verbosity
|> `?` to see other options
------------------------------------------------------------------------
Learn something new with every build...
|> See last logs of a build with `nix log --last` command.
------------------------------------------------------------------------
Evaluated my-project 1.2.3 in 14.43 seconds
Downloading [12 / 200]
|> firefox 1.2.3 [#########> ] 10Mb/s | 2min left
Building [2 / 20]
|> glibc 1.2.3 -> buildPhase: <last log line>
------------------------------------------------------------------------
```
Now **Learn** part of the output is where you educate users. You should only
show it when you know that a build will take some time and not annoy users of
the builds that take only few seconds.
Every feature like this should go through an intensive review and testing to
collect as much feedback as possible and to fine tune every little detail. If
done right this can be an awesome features beginners and advance users will
love, but if not done perfectly it will annoy users and leave bad impression.
# Input
Input to a command is provided via `ARGUMENTS` and `OPTIONS`.
`ARGUMENTS` represent a required input for a function. When choosing to use
`ARGUMENTS` over `OPTIONS` please be aware of the downsides that come with it:
- User will need to remember the order of `ARGUMENTS`. This is not a problem if
there is only one `ARGUMENT`.
- With `OPTIONS` it is possible to provide much better auto completion.
- With `OPTIONS` it is possible to provide much better error message.
- Using `OPTIONS` it will mean there is a little bit more typing.
We don’t discourage the use of `ARGUMENTS`, but simply want to make every
developer consider the downsides and choose wisely.
## Naming the `OPTIONS`
The only naming convention - apart from the ones mentioned in Naming the
`COMMANDS` section is how flags are named.
Flags are a type of `OPTION` that represent an option that can be turned ON of
OFF. We can say **flags are boolean type of** `**OPTION**`.
Here are few examples of flag `OPTIONS`:
- `--colors` vs. `--no-colors` (showing colors in the output)
- `--emojis` vs. `--no-emojis` (showing emojis in the output)
## Prompt when input not provided
For *main commands* (as [per classification](#classification)) we want command
to improve the discoverability of possible input. A new user will most likely
not know which `ARGUMENTS` and `OPTIONS` are required or which values are
possible for those options.
In case the user does not provide the input or they provide wrong input,
rather than show the error, prompt a user with an option to find and select
correct input (see examples).
Prompting is of course not required when TTY is not attached to STDIN. This
would mean that scripts won't need to handle prompt, but rather handle errors.
A place to use prompt and provide user with interactive select
```shell
$ nix init
Initializing Nix project at `/path/to/here`.
Select a template for you new project:
|> py
template#python-pip
template#python-poetry
[ Showing 2 templates from 1345 templates ]
```
Another great place to add prompts are **confirmation dialogues for dangerous
actions**. For example when adding new substitutor via `OPTIONS` or via
`flake.nix` we should prompt - for the first time - and let user review what is
going to happen.
```shell
$ nix build --option substitutors https://cache.example.org
------------------------------------------------------------------------
Warning! A security related question needs to be answered.
------------------------------------------------------------------------
The following substitutors will be used to in `my-project`:
- https://cache.example.org
Do you allow `my-project` to use above mentioned substitutors?
[y/N] |> y
```
# Output
Terminal output can be quite limiting in many ways. Which should force us to
think about the experience even more. As with every design the output is a
compromise between being terse and being verbose, between showing help to
beginners and annoying advance users. For this it is important that we know
what are the priorities.
Nix command line should be first and foremost written with beginners in mind.
But users won't stay beginners for long and what was once useful might quickly
become annoying. There is no golden rule that we can give in this guideline
that would make it easier how to draw a line and find best compromise.
What we would encourage is to **build prototypes**, do some **user testing**
and collect **feedback**. Then repeat the cycle few times.
First design the *happy path* and only after your iron it out, continue to work
on **edge cases** (handling and displaying errors, changes of the output by
certain `OPTIONS`, etc…)
## Follow best practices
Needless to say we Nix must be a good citizen and follow best practices in
command line.
In short: **STDOUT is for output, STDERR is for (human) messaging.**
STDOUT and STDERR provide a way for you to output messages to the user while
also allowing them to redirect content to a file. For example:
```shell
$ nix build > build.txt
------------------------------------------------------------------------
Error! Attribute `bin` missing at (1:94) from string.
------------------------------------------------------------------------
1| with import <nixpkgs> { }; (pkgs.runCommandCC or pkgs.runCommand) "shell" { buildInputs = [ (surge.bin) ]; } ""
```
Because this warning is on STDERR, it doesn’t end up in the file.
But not everything on STDERR is an error though. For example, you can run `nix
build` and collect logs in a file while still seeing the progress.
```
$ nix build > build.txt
Evaluated 1234 files in 1.2 seconds
Downloaded python3.8-poetry 1.2.3 in 5.3 seconds
Downloaded python3.8-requests 1.2.3 in 5.3 seconds
------------------------------------------------------------------------
Press `v` to increase logs verbosity
|> `?` to see other options
------------------------------------------------------------------------
Learn something new with every build...
|> See last logs of a build with `nix log --last` command.
------------------------------------------------------------------------
Evaluated my-project 1.2.3 in 14.43 seconds
Downloading [12 / 200]
|> firefox 1.2.3 [#########> ] 10Mb/s | 2min left
Building [2 / 20]
|> glibc 1.2.3 -> buildPhase: <last log line>
------------------------------------------------------------------------
```
## Errors (WIP)
**TODO**: Once we have implementation for the *happy path* then we will think
how to present errors.
## Not only for humans
Terse, machine-readable output formats can also be useful but shouldn’t get in
the way of making beautiful CLI output. When needed, commands should offer a
`--json` flag to allow users to easily parse and script the CLI.
When TTY is not detected on STDOUT we should remove all design elements (no
colors, no emojis and using ASCII instead of Unicode symbols). The same should
happen when TTY is not detected on STDERR. We should not display progress /
status section, but only print warnings and errors.
## Dialog with the user
CLIs don't always make it clear when an action has taken place. For every
action a user performs, your CLI should provide an equal and appropriate
reaction, clearly highlighting the what just happened. For example:
```shell
$ nix build
Downloaded python3.8-poetry 1.2.3 in 5.3 seconds
Downloaded python3.8-requests 1.2.3 in 5.3 seconds
...
Success! You have successfully built my-project.
$
```
Above command clearly states that command successfully completed. And in case
of `nix build`, which is a command that might take some time to complete, it is
equally important to also show that a command started.
## Text alignment
Text alignment is the number one design element that will present all of the
Nix commands as a family and not as separate tools glued together.
The format we should follow is:
```shell
$ nix COMMAND
VERB_1 NOUN and other words
VERB__1 NOUN and other words
|> Some details
```
Few rules that we can extract from above example:
- Each line should start at least with one space.
- First word should be a VERB and must be aligned to the right.
- Second word should be a NOUN and must be aligned to the left.
- If you can not find a good VERB / NOUN pair, don’t worry make it as
understandable to the user as possible.
- More details of each line can be provided by `|>` character which is serving
as the first word when aligning the text
Don’t forget you should also test your terminal output with colors and emojis
off (`--no-colors --no-emojis`).
## Dim / Bright
After comparing few terminals with different color schemes we would **recommend
to avoid using dimmed text**. The difference from the rest of the text is very
little in many terminal and color scheme combinations. Sometimes the difference
is not even notable, therefore relying on it wouldn’t make much sense.
**The bright text is much better supported** across terminals and color
schemes. Most of the time the difference is perceived as if the bright text
would be bold.
## Colors
Humans are already conditioned by society to attach certain meaning to certain
colors. While the meaning is not universal, a simple collection of colors is
used to represent basic emotions.
Colors that can be used in output
- Red = error, danger, stop
- Green = success, good
- Yellow/Orange = proceed with caution, warning, in progress
- Blue/Magenta = stability, calm
While colors are nice, when command line is used by machines (in automation
scripts) you want to remove the colors. There should be a global `--no-colors`
option that would remove the colors.
## Special (Unicode) characters
Most of the terminal have good support for Unicode characters and you should
use them in your output by default. But always have a backup solution that is
implemented only with ASCII characters and will be used when `--ascii` option
is going to be passed in. Please make sure that you test your output also
without Unicode characters
More they showing all the different Unicode characters it is important to
**establish common set of characters** that we use for certain situations.
## Emojis
Emojis help channel emotions even better than text, colors and special
characters.
We recommend **keeping the set of emojis to a minimum**. This will enable each
emoji to stand out more.
As not everybody is happy about emojis we should provide an `--no-emojis`
option to disable them. Please make sure that you test your output also without
emojis.
## Tables
All commands that are listing certain data can be implemented in some sort of a
table. It’s important that each row of your output is a single ‘entry’ of data.
Never output table borders. It’s noisy and a huge pain for parsing using other
tools such as `grep`.
Be mindful of the screen width. Only show a few columns by default with the
table header, for more the table can be manipulated by the following options:
- `--no-headers`: Show column headers by default but allow to hide them.
- `--columns`: Comma-separated list of column names to add.
- `--sort`: Allow sorting by column. Allow inverse and multi-column sort as well.
## Interactive output
Interactive output was selected to be able to strike the balance between
beginners and advance users. While the default output will target beginners it
can, with a few key strokes, be changed into and advance introspection tool.
### Progress
For longer running commands we should provide and overview the progress.
This is shown best in `nix build` example:
```shell
$ nix build
Started building my-project 1.2.3
Downloaded python3.8-poetry 1.2.3 in 5.3 seconds
Downloaded python3.8-requests 1.2.3 in 5.3 seconds
------------------------------------------------------------------------
Press `v` to increase logs verbosity
|> `?` to see other options
------------------------------------------------------------------------
Learn something new with every build...
|> See last logs of a build with `nix log --last` command.
------------------------------------------------------------------------
Evaluated my-project 1.2.3 in 14.43 seconds
Downloading [12 / 200]
|> firefox 1.2.3 [#########> ] 10Mb/s | 2min left
Building [2 / 20]
|> glibc 1.2.3 -> buildPhase: <last log line>
------------------------------------------------------------------------
```
### Search
Use a `fzf` like fuzzy search when there are multiple options to choose from.
```shell
$ nix init
Initializing Nix project at `/path/to/here`.
Select a template for you new project:
|> py
template#python-pip
template#python-poetry
[ Showing 2 templates from 1345 templates ]
```
### Prompt
In some situations we need to prompt the user and inform the user about what is
going to happen.
```shell
$ nix build --option substitutors https://cache.example.org
------------------------------------------------------------------------
Warning! A security related question needs to be answered.
------------------------------------------------------------------------
The following substitutors will be used to in `my-project`:
- https://cache.example.org
Do you allow `my-project` to use above mentioned substitutors?
[y/N] |> y
```
## Verbosity
There are many ways that you can control verbosity.
Verbosity levels are:
- `ERROR` (level 0)
- `WARN` (level 1)
- `NOTICE` (level 2)
- `INFO` (level 3)
- `TALKATIVE` (level 4)
- `CHATTY` (level 5)
- `DEBUG` (level 6)
- `VOMIT` (level 7)
The default level that the command starts is `ERROR`. The simplest way to
increase the verbosity by stacking `-v` option (eg: `-vvv == level 3 == INFO`).
There are also two shortcuts, `--debug` to run in `DEBUG` verbosity level and
`--quiet` to run in `ERROR` verbosity level.
----------
# Appendix 1: Commands naming exceptions
`nix init` and `nix repl` are well established

79
doc/manual/source/development/contributing.md Normal file
View file

@ -0,0 +1,79 @@
# Contributing
## Add a release note
`doc/manual/rl-next` contains release notes entries for all unreleased changes.
User-visible changes should come with a release note.
### Add an entry
Here's what a complete entry looks like. The file name is not incorporated in the document.
```
---
synopsis: Basically a title
issues: 1234
prs: 1238
---
Here's one or more paragraphs that describe the change.
- It's markdown
- Add references to the manual using @docroot@
```
Significant changes should add the following header, which moves them to the top.
```
significance: significant
```
<!-- Keep an eye on https://codeberg.org/fgaz/changelog-d/issues/1 -->
See also the [format documentation](https://github.com/haskell/cabal/blob/master/CONTRIBUTING.md#changelog).
### Build process
Releases have a precomputed `rl-MAJOR.MINOR.md`, and no `rl-next.md`.
## Branches
- [`master`](https://github.com/NixOS/nix/commits/master)
The main development branch. All changes are approved and merged here.
When developing a change, create a branch based on the latest `master`.
Maintainers try to [keep it in a release-worthy state](#reverting).
- [`maintenance-*.*`](https://github.com/NixOS/nix/branches/all?query=maintenance)
These branches are the subject of backports only, and are
also [kept](#reverting) in a release-worthy state.
See [`maintainers/backporting.md`](https://github.com/NixOS/nix/blob/master/maintainers/backporting.md)
- [`latest-release`](https://github.com/NixOS/nix/tree/latest-release)
The latest patch release of the latest minor version.
See [`maintainers/release-process.md`](https://github.com/NixOS/nix/blob/master/maintainers/release-process.md)
- [`backport-*-to-*`](https://github.com/NixOS/nix/branches/all?query=backport)
Generally branches created by the backport action.
See [`maintainers/backporting.md`](https://github.com/NixOS/nix/blob/master/maintainers/backporting.md)
- [_other_](https://github.com/NixOS/nix/branches/all)
Branches that do not conform to the above patterns should be feature branches.
## Reverting
If a change turns out to be merged by mistake, or contain a regression, it may be reverted.
A revert is not a rejection of the contribution, but merely part of an effective development process.
It makes sure that development keeps running smoothly, with minimal uncertainty, and less overhead.
If maintainers have to worry too much about avoiding reverts, they would not be able to merge as much.
By embracing reverts as a good part of the development process, everyone wins.
However, taking a step back may be frustrating, so maintainers will be extra supportive on the next try.

28
doc/manual/source/development/cxx.md Normal file
View file

@ -0,0 +1,28 @@
# C++ style guide
Some miscellaneous notes on how we write C++.
Formatting we hope to eventually normalize automatically, so this section is free to just discuss higher-level concerns.
## The `*-impl.hh` pattern
Let's start with some background info first.
Headers, are supposed to contain declarations, not definitions.
This allows us to change a definition without changing the declaration, and have a very small rebuild during development.
Templates, however, need to be specialized to use-sites.
Absent fancier techniques, templates require that the definition, not just mere declaration, must be available at use-sites in order to make that specialization on the fly as part of compiling those use-sites.
Making definitions available like that means putting them in headers, but that is unfortunately means we get all the extra rebuilds we want to avoid by just putting declarations there as described above.
The `*-impl.hh` pattern is a ham-fisted partial solution to this problem.
It constitutes:
- Declaring items only in the main `foo.hh`, including templates.
- Putting template definitions in a companion `foo-impl.hh` header.
Most C++ developers would accompany this by having `foo.hh` include `foo-impl.hh`, to ensure any file getting the template declarations also got the template definitions.
But we've found not doing this has some benefits and fewer than imagined downsides.
The fact remains that headers are rarely as minimal as they could be;
there is often code that needs declarations from the headers but not the templates within them.
With our pattern where `foo.hh` doesn't include `foo-impl.hh`, that means they can just include `foo.hh`
Code that needs both just includes `foo.hh` and `foo-impl.hh`.
This does make linking error possible where something forgets to include `foo-impl.hh` that needs it, but those are build-time only as easy to fix.

62
doc/manual/source/development/debugging.md Normal file
View file

@ -0,0 +1,62 @@
# Debugging Nix
This section shows how to build and debug Nix with debug symbols enabled.
## Building Nix with Debug Symbols
In the development shell, set the `mesonBuildType` environment variable to `debug` before configuring the build:
```console
[nix-shell]$ export mesonBuildType=debugoptimized
```
Then, proceed to build Nix as described in [Building Nix](./building.md).
This will build Nix with debug symbols, which are essential for effective debugging.
## Debugging the Nix Binary
Obtain your preferred debugger within the development shell:
```console
[nix-shell]$ nix-shell -p gdb
```
On macOS, use `lldb`:
```console
[nix-shell]$ nix-shell -p lldb
```
### Launching the Debugger
To debug the Nix binary, run:
```console
[nix-shell]$ gdb --args ../outputs/out/bin/nix
```
On macOS, use `lldb`:
```console
[nix-shell]$ lldb -- ../outputs/out/bin/nix
```
### Using the Debugger
Inside the debugger, you can set breakpoints, run the program, and inspect variables.
```gdb
(gdb) break main
(gdb) run <arguments>
```
Refer to the [GDB Documentation](https://www.gnu.org/software/gdb/documentation/) for comprehensive usage instructions.
On macOS, use `lldb`:
```lldb
(lldb) breakpoint set --name main
(lldb) process launch -- <arguments>
```
Refer to the [LLDB Tutorial](https://lldb.llvm.org/use/tutorial.html) for comprehensive usage instructions.

231
doc/manual/source/development/documentation.md Normal file
View file

@ -0,0 +1,231 @@
# Contributing documentation
Improvements to documentation are very much appreciated, and a good way to start out with contributing to Nix.
This is how you can help:
- Address [open issues with documentation](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+label%3Adocumentation)
- Review [pull requests concerning documentation](https://github.com/NixOS/nix/pulls?q=is%3Apr+is%3Aopen+label%3Adocumentation)
Incremental refactorings of the documentation build setup to make it faster or easier to understand and maintain are also welcome.
## Building the manual
Build the manual from scratch:
```console
nix-build -E '(import ./.).packages.${builtins.currentSystem}.nix.doc'
```
or
```console
nix build .#nix-manual
```
and open `./result/share/doc/nix/manual/index.html`.
To build the manual incrementally, [enter the development shell](./building.md) and run:
```console
make manual-html-open -j $NIX_BUILD_CORES
```
In order to reflect changes to the [Makefile for the manual], clear all generated files before re-building:
[Makefile for the manual]: https://github.com/NixOS/nix/blob/master/doc/manual/local.mk
```console
rm $(git ls-files doc/manual/ -o | grep -F '.md') && rmdir doc/manual/source/command-ref/new-cli && make manual-html -j $NIX_BUILD_CORES
```
## Style guide
The goal of this style guide is to make it such that
- The manual is easy to search and skim for relevant information
- Documentation sources are easy to edit
- Changes to documentation are easy to review
You will notice that this is not implemented consistently yet.
Please follow the guide when making additions or changes to existing documentation.
Do not make sweeping changes, unless they are programmatic and can be validated easily.
### Language
This manual is [reference documentation](https://diataxis.fr/reference/).
The typical usage pattern is to look up isolated pieces of information.
It should therefore aim to be correct, consistent, complete, and easy to navigate at a glance.
- Aim for clarity and brevity.
Please take the time to read the [plain language guidelines](https://www.plainlanguage.gov/guidelines/) for details.
- Describe the subject factually.
In particular, do not make value judgements or recommendations.
Check the code or add tests if in doubt.
- Provide complete, minimal examples, and explain them.
Readers should be able to try examples verbatim and get the same results as shown in the manual.
Always describe in words what a given example does.
Non-trivial examples may need additional explanation, especially if they use concepts from outside the given context.
- Always explain code examples in the text.
Use comments in code samples very sparingly, for instance to highlight a particular aspect.
Readers tend to glance over large amounts of code when scanning for information.
Especially beginners will likely find reading more complex-looking code strenuous and may therefore avoid it altogether.
If a code sample appears to require a lot of inline explanation, consider replacing it with a simpler one.
If that's not possible, break the example down into multiple parts, explain them separately, and then show the combined result at the end.
This should be a last resort, as that would amount to writing a [tutorial](https://diataxis.fr/tutorials/) on the given subject.
- Use British English.
This is a somewhat arbitrary choice to force consistency, and accounts for the fact that a majority of Nix users and developers are from Europe.
### Links and anchors
Reference documentation must be readable in arbitrary order.
Readers cannot be expected to have any particular prerequisite knowledge about Nix.
While the table of contents can provide guidance and full-text search can help, they are most likely to find what they need by following sensible cross-references.
- Link to technical terms
When mentioning Nix-specific concepts, commands, options, settings, etc., link to appropriate documentation.
Also link to external tools or concepts, especially if their meaning may be ambiguous.
You may also want to link to definitions of less common technical terms.
Then readers won't have to actively search for definitions and are more likely to discover relevant information on their own.
> **Note**
>
> `man` and `--help` pages don't display links.
> Use appropriate link texts such that readers of terminal output can infer search terms.
- Do not break existing URLs between releases.
There are countless links in the wild pointing to old versions of the manual.
We want people to find up-to-date documentation when following popular advice.
- When moving files, update [redirects on nixos.org](https://github.com/NixOS/nixos-homepage/blob/master/netlify.toml).
This is especially important when moving information out of the Nix manual to other resources.
- When changing anchors, update [client-side redirects](https://github.com/NixOS/nix/blob/master/doc/manual/redirects.js)
The current setup is cumbersome, and help making better automation is appreciated.
The build checks for broken internal links with.
This happens late in the process, so [building the whole manual](#building-the-manual) is not suitable for iterating quickly.
[`mdbook-linkcheck`] does not implement checking [URI fragments] yet.
[`mdbook-linkcheck`]: https://github.com/Michael-F-Bryan/mdbook-linkcheck
[URI fragments]: https://en.wikipedia.org/wiki/URI_fragment
### Markdown conventions
The manual is written in markdown, and rendered with [mdBook](https://github.com/rust-lang/mdBook) for the web and with [lowdown](https://github.com/kristapsdz/lowdown) for `man` pages and `--help` output.
For supported markdown features, refer to:
- [mdBook documentation](https://rust-lang.github.io/mdBook/format/markdown.html)
- [lowdown documentation](https://kristaps.bsd.lv/lowdown/)
Please observe these guidelines to ease reviews:
- Write one sentence per line.
This makes long sentences immediately visible, and makes it easier to review changes and make direct suggestions.
- Use reference links – sparingly – to ease source readability.
Put definitions close to their first use.
Example:
```
A [store object] contains a [file system object] and [references] to other store objects.
[store object]: @docroot@/store/store-object.md
[file system object]: @docroot@/architecture/file-system-object.md
[references]: @docroot@/glossary.md#gloss-reference
```
- Use admonitions of the following form:
```
> **Note**
>
> This is a note.
```
Highlight examples as such:
````
> **Example**
>
> ```console
> $ nix --version
> ```
````
Highlight syntax definitions as such, using [EBNF](https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_form) notation:
````
> **Syntax**
>
> *attribute-set* = `{` [ *attribute-name* `=` *expression* `;` ... ] `}`
````
### The `@docroot@` variable
`@docroot@` provides a base path for links that occur in reusable snippets or other documentation that doesn't have a base path of its own.
If a broken link occurs in a snippet that was inserted into multiple generated files in different directories, use `@docroot@` to reference the `doc/manual/source` directory.
If the `@docroot@` literal appears in an error message from the [`mdbook-linkcheck`] tool, the `@docroot@` replacement needs to be applied to the generated source file that mentions it.
See existing `@docroot@` logic in the [Makefile for the manual].
Regular markdown files used for the manual have a base path of their own and they can use relative paths instead of `@docroot@`.
## API documentation
[Doxygen API documentation] is available online.
You can also build and view it yourself:
[Doxygen API documentation]: https://hydra.nixos.org/job/nix/master/internal-api-docs/latest/download-by-type/doc/internal-api-docs
```console
$ nix build .#hydraJobs.internal-api-docs
$ xdg-open ./result/share/doc/nix/internal-api/html/index.html
```
or inside `nix-shell` or `nix develop`:
```console
$ configurePhase
$ ninja src/internal-api-docs/html
$ xdg-open src/internal-api-docs/html/index.html
```
## C API documentation
Note that the C API is not yet stable.
[C API documentation] is available online.
You can also build and view it yourself:
[C API documentation]: https://hydra.nixos.org/job/nix/master/external-api-docs/latest/download-by-type/doc/external-api-docs
```console
$ nix build .#hydraJobs.external-api-docs
$ xdg-open ./result/share/doc/nix/external-api/html/index.html
```
or inside `nix-shell` or `nix develop`:
```
$ configurePhase
$ ninja src/external-api-docs/html
$ xdg-open src/external-api-docs/html/index.html
```

95
doc/manual/source/development/experimental-features.md Normal file
View file

@ -0,0 +1,95 @@
This section describes the notion of *experimental features*, and how it fits into the big picture of the development of Nix.
# What are experimental features?
Experimental features are considered unstable, which means that they can be changed or removed at any time.
Users must explicitly enable them by toggling the associated [experimental feature flags](@docroot@/command-ref/conf-file.md#conf-experimental-features).
This allows accessing unstable functionality without unwittingly relying on it.
Experimental feature flags were first introduced in [Nix 2.4](@docroot@/release-notes/rl-2.4.md).
Before that, Nix did have experimental features, but they were not guarded by flags and were merely documented as unstable.
This was a source of confusion and controversy.
# When should a new feature be marked experimental?
A change in the Nix codebase should be guarded by an experimental feature flag if it is considered likely to be reverted or adapted in a backwards-incompatible manner after gathering more experience with it in practice.
Examples:
- Changes to the Nix language, such as new built-ins, syntactic or semantic changes, etc.
- Changes to the command-line interface
# Lifecycle of an experimental feature
Experimental features have to be treated on a case-by-case basis.
However, the standard workflow for an experimental feature is as follows:
- A new feature is implemented in a *pull request*
- It is guarded by an experimental feature flag that is disabled by default
- The pull request is merged, the *experimental* feature ends up in a release
- Using the feature requires explicitly enabling it, signifying awareness of the potential risks
- Being experimental, the feature can still be changed arbitrarily
- The feature can be *removed*
- The associated experimental feature flag is also removed
- The feature can be declared *stable*
- The associated experimental feature flag is removed
- There should be enough evidence of users having tried the feature, such as feedback, fixed bugs, demonstrations of how it is put to use
- Maintainers must feel confident that:
- The feature is designed and implemented sensibly, that it is fit for purpose
- Potential interactions are well-understood
- Stabilising the feature will not incur an outsized maintenance burden in the future
The following diagram illustrates the process:
```
.------.
| idea |
'------'
|
discussion, design, implementation
|
| .-------.
| | |
v v |
.--------------. review
| pull request | |
'--------------' |
| ^ | |
| | '-------'
.---' '----.
| |
merge user feedback,
| (breaking) changes
| |
'---. .----'
| |
v |
+--------------+
.---| experimental |----.
| +--------------+ |
| |
decision to stabilise decision against
| keeping the feature
| |
v v
+--------+ +---------+
| stable | | removed |
+--------+ +---------+
```
# Relation to the RFC process
Experimental features and [RFCs](https://github.com/NixOS/rfcs/) both allow approaching substantial changes while minimizing the risk.
However they serve different purposes:
- An experimental feature enables developers to iterate on and deliver a new idea without committing to it or requiring a costly long-running fork.
It is primarily an issue of *implementation*, targeting Nix developers and early testers.
- The goal of an RFC is to make explicit all the implications of a change:
Explain why it is wanted, which new use-cases it enables, which interface changes it requires, etc.
It is primarily an issue of *design* and *communication*, targeting the broader community.
This means that experimental features and RFCs are orthogonal mechanisms, and can be used independently or together as needed.
# Currently available experimental features
{{#include ./experimental-feature-descriptions.md}}

8
doc/manual/source/development/index.md Normal file
View file

@ -0,0 +1,8 @@
# Development
Nix is developed on GitHub.
Check the [contributing guide](https://github.com/NixOS/nix/blob/master/CONTRIBUTING.md) if you want to get involved.
This chapter is a collection of guides for making changes to the code and documentation.
If you're not sure where to start, try to [compile Nix from source](./building.md) and consider [making improvements to documentation](./documentation.md).

128
doc/manual/source/development/json-guideline.md Normal file
View file

@ -0,0 +1,128 @@
# JSON guideline
Nix consumes and produces JSON in a variety of contexts.
These guidelines ensure consistent practices for all our JSON interfaces, for ease of use, and so that experience in one part carries over to another.
## Extensibility
The schema of JSON input and output should allow for backwards compatible extension.
This section explains how to achieve this.
Two definitions are helpful here, because while JSON only defines one "key-value" object type, we use it to cover two use cases:
- **dictionary**: a map from names to value that all have the same type.
In C++ this would be a `std::map` with string keys.
- **record**: a fixed set of attributes each with their own type.
In C++, this would be represented by a `struct`.
It is best not to mix these use cases, as that may lead to incompatibilities when the schema changes.
For example, adding a record field to a dictionary breaks consumers that assume all JSON object fields to have the same meaning and type, and dictionary items with a colliding name can not be represented anymore.
This leads to the following guidelines:
- The top-level (root) value must be a record.
Otherwise, one can not change the structure of a command's output.
- The value of a dictionary item must be a record.
Otherwise, the item type can not be extended.
- List items should be records.
Otherwise, one can not change the structure of the list items.
If the order of the items does not matter, and each item has a unique key that is a string, consider representing the list as a dictionary instead.
If the order of the items needs to be preserved, return a list of records.
- Streaming JSON should return records.
An example of a streaming JSON format is [JSON lines](https://jsonlines.org/), where each line represents a JSON value.
These JSON values can be considered top-level values or list items, and they must be records.
### Examples
This is bad, because all keys must be assumed to be store types:
```json
{
"local": { ... },
"remote": { ... },
"http": { ... }
}
```
This is good, because the it is extensible at the root, and is somewhat self-documenting:
```json
{
"storeTypes": { "local": { ... }, ... },
"pluginSupport": true
}
```
While the dictionary of store types seems like a very complete response at first, a use case may arise that warrants returning additional information.
For example, the presence of plugin support may be crucial information for a client to proceed when their desired store type is missing.
The following representation is bad because it is not extensible:
```json
{ "outputs": [ "out" "bin" ] }
```
However, simply converting everything to records is not enough, because the order of outputs must be preserved:
```json
{ "outputs": { "bin": {}, "out": {} } }
```
The first item is the default output. Deriving this information from the outputs ordering is not great, but this is how Nix currently happens to work.
While it is possible for a JSON parser to preserve the order of fields, we can not rely on this capability to be present in all JSON libraries.
This representation is extensible and preserves the ordering:
```json
{ "outputs": [ { "outputName": "out" }, { "outputName": "bin" } ] }
```
## Self-describing values
As described in the previous section, it's crucial that schemas can be extended with new fields without breaking compatibility.
However, that should *not* mean we use the presence/absence of fields to indicate optional information *within* a version of the schema.
Instead, always include the field, and use `null` to indicate the "nothing" case.
### Examples
Here are two JSON objects:
```json
{
"foo": {}
}
```
```json
{
"foo": {},
"bar": {}
}
```
Since they differ in which fields they contain, they should *not* both be valid values of the same schema.
At most, they can match two different schemas where the second (with `foo` and `bar`) is considered a newer version of the first (with just `foo`).
Within each version, all fields are mandatory (always `foo`, and always `foo` and `bar`).
Only *between* each version, `bar` gets added as a new mandatory field.
Here are another two JSON objects:
```json
{ "foo": null }
```
```json
{ "foo": { "bar": 1 } }
```
Since they both contain a `foo` field, they could be valid values of the same schema.
The schema would have `foo` has an optional field, which is either `null` or an object where `bar` is an integer.

12
doc/manual/source/development/meson.build Normal file
View file

@ -0,0 +1,12 @@
experimental_feature_descriptions_md = custom_target(
command : nix_eval_for_docs + [
'--expr',
'import @INPUT0@ (builtins.fromJSON (builtins.readFile @INPUT1@))',
],
input : [
'../../generate-xp-features.nix',
xp_features_json,
],
capture : true,
output : 'experimental-feature-descriptions.md',
)

358
doc/manual/source/development/testing.md Normal file
View file

@ -0,0 +1,358 @@
# Running tests
## Coverage analysis
A [coverage analysis report] is available online
You can build it yourself:
[coverage analysis report]: https://hydra.nixos.org/job/nix/master/coverage/latest/download-by-type/report/coverage
```
# nix build .#hydraJobs.coverage
# xdg-open ./result/coverage/index.html
```
[Extensive records of build metrics](https://hydra.nixos.org/job/nix/master/coverage#tabs-charts), such as test coverage over time, are also available online.
## Unit-tests
The unit tests are defined using the [googletest] and [rapidcheck] frameworks.
[googletest]: https://google.github.io/googletest/
[rapidcheck]: https://github.com/emil-e/rapidcheck
[property testing]: https://en.wikipedia.org/wiki/Property_testing
### Source and header layout
> An example of some files, demonstrating much of what is described below
>
> ```
> src
> ├── libexpr
> │ ├── meson.build
> │ ├── value/context.hh
> │ ├── value/context.cc
> │ …
> │
> ├── tests
> │ │
> │ …
> │ ├── libutil-tests
> │ │ ├── meson.build
> │ │ …
> │ │ └── data
> │ │ ├── git/tree.txt
> │ │ …
> │ │
> │ ├── libexpr-test-support
> │ │ ├── meson.build
> │ │ └── tests
> │ │ ├── value/context.hh
> │ │ ├── value/context.cc
> │ │ …
> │ │
> │ ├── libexpr-tests
> │ … ├── meson.build
> │ ├── value/context.cc
> │ …
> …
> ```
The tests for each Nix library (`libnixexpr`, `libnixstore`, etc..) live inside a directory `src/${library_name_without-nix}-test`.
Given an interface (header) and implementation pair in the original library, say, `src/libexpr/value/context.{hh,cc}`, we write tests for it in `src/libexpr-tests/value/context.cc`, and (possibly) declare/define additional interfaces for testing purposes in `src/libexpr-test-support/tests/value/context.{hh,cc}`.
Data for unit tests is stored in a `data` subdir of the directory for each unit test executable.
For example, `libnixstore` code is in `src/libstore`, and its test data is in `src/libstore-tests/data`.
The path to the `src/${library_name_without-nix}-test/data` directory is passed to the unit test executable with the environment variable `_NIX_TEST_UNIT_DATA`.
Note that each executable only gets the data for its tests.
The unit test libraries are in `src/${library_name_without-nix}-test-support`.
All headers are in a `tests` subdirectory so they are included with `#include "tests/"`.
The use of all these separate directories for the unit tests might seem inconvenient, as for example the tests are not "right next to" the part of the code they are testing.
But organizing the tests this way has one big benefit:
there is no risk of any build-system wildcards for the library accidentally picking up test code that should not built and installed as part of the library.
### Running tests
You can run the whole testsuite with `meson test` from the Meson build directory, or the tests for a specific component with `meson test nix-store-tests`.
A environment variables that Google Test accepts are also worth knowing:
1. [`GTEST_FILTER`](https://google.github.io/googletest/advanced.html#running-a-subset-of-the-tests)
This is used for finer-grained filtering of which tests to run.
2. [`GTEST_BRIEF`](https://google.github.io/googletest/advanced.html#suppressing-test-passes)
This is used to avoid logging passing tests.
Putting the two together, one might run
```bash
GTEST_BRIEF=1 GTEST_FILTER='ErrorTraceTest.*' meson test nix-expr-tests -v
```
for short but comprensive output.
### Characterisation testing { #characaterisation-testing-unit }
See [functional characterisation testing](#characterisation-testing-functional) for a broader discussion of characterisation testing.
Like with the functional characterisation, `_NIX_TEST_ACCEPT=1` is also used.
For example:
```shell-session
$ _NIX_TEST_ACCEPT=1 meson test nix-store-tests -v
...
[ SKIPPED ] WorkerProtoTest.string_read
[ SKIPPED ] WorkerProtoTest.string_write
[ SKIPPED ] WorkerProtoTest.storePath_read
[ SKIPPED ] WorkerProtoTest.storePath_write
...
```
will regenerate the "golden master" expected result for the `libnixstore` characterisation tests.
The characterisation tests will mark themselves "skipped" since they regenerated the expected result instead of actually testing anything.
### Unit test support libraries
There are headers and code which are not just used to test the library in question, but also downstream libraries.
For example, we do [property testing] with the [rapidcheck] library.
This requires writing `Arbitrary` "instances", which are used to describe how to generate values of a given type for the sake of running property tests.
Because types contain other types, `Arbitrary` "instances" for some type are not just useful for testing that type, but also any other type that contains it.
Downstream types frequently contain upstream types, so it is very important that we share arbitrary instances so that downstream libraries' property tests can also use them.
It is important that these testing libraries don't contain any actual tests themselves.
On some platforms they would be run as part of every test executable that uses them, which is redundant.
On other platforms they wouldn't be run at all.
## Functional tests
The functional tests reside under the `tests/functional` directory and are listed in `tests/functional/meson.build`.
Each test is a bash script.
Functional tests are run during `installCheck` in the `nix` package build, as well as separately from the build, in VM tests.
### Running the whole test suite
The whole test suite (functional and unit tests) can be run with:
```shell-session
$ checkPhase
```
### Grouping tests
Sometimes it is useful to group related tests so they can be easily run together without running the entire test suite.
Each test group is in a subdirectory of `tests`.
For example, `tests/functional/ca/meson.build` defines a `ca` test group for content-addressed derivation outputs.
That test group can be run like this:
```shell-session
$ meson test --suite ca
ninja: Entering directory `/home/jcericson/src/nix/master/build'
ninja: no work to do.
[1-20/20] 🌑 nix-functional-tests:ca / ca/why-depends 1/20 nix-functional-tests:ca / ca/nix-run OK 0.16s
[2-20/20] 🌒 nix-functional-tests:ca / ca/why-depends 2/20 nix-functional-tests:ca / ca/import-derivation OK 0.17s
```
### Running individual tests
Individual tests can be run with `meson`:
```shell-session
$ meson test --verbose ${testName}
ninja: Entering directory `/home/jcericson/src/nix/master/build'
ninja: no work to do.
1/1 nix-functional-tests:main / ${testName} OK 0.41s
Ok: 1
Expected Fail: 0
Fail: 0
Unexpected Pass: 0
Skipped: 0
Timeout: 0
Full log written to /home/jcericson/src/nix/master/build/meson-logs/testlog.txt
```
The `--verbose` flag will make Meson also show the console output of each test for easier debugging.
The test script will then be traced with `set -x` and the output displayed as it happens,
regardless of whether the test succeeds or fails.
Tests can be also run directly without `meson`:
```shell-session
$ TEST_NAME=${testName} NIX_REMOTE='' PS4='+(${BASH_SOURCE[0]-$0}:$LINENO) tests/functional/${testName}.sh
+(${testName}.sh:1) foo
output from foo
+(${testName}.sh:2) bar
output from bar
...
```
### Debugging failing functional tests
When a functional test fails, it usually does so somewhere in the middle of the script.
To figure out what's wrong, it is convenient to run the test regularly up to the failing `nix` command, and then run that command with a debugger like GDB.
For example, if the script looks like:
```bash
foo
nix blah blub
bar
```
edit it like so:
```diff
foo
-nix blah blub
+gdb --args nix blah blub
bar
```
Then, running the test with `./mk/debug-test.sh` will drop you into GDB once the script reaches that point:
```shell-session
$ ./mk/debug-test.sh tests/functional/${testName}.sh
...
+ gdb blash blub
GNU gdb (GDB) 12.1
...
(gdb)
```
One can debug the Nix invocation in all the usual ways.
For example, enter `run` to start the Nix invocation.
### Troubleshooting
Sometimes running tests in the development shell may leave artefacts in the local repository.
To remove any traces of that:
```console
git clean -x --force tests
```
### Characterisation testing { #characterisation-testing-functional }
Occasionally, Nix utilizes a technique called [Characterisation Testing](https://en.wikipedia.org/wiki/Characterization_test) as part of the functional tests.
This technique is to include the exact output/behavior of a former version of Nix in a test in order to check that Nix continues to produce the same behavior going forward.
For example, this technique is used for the language tests, to check both the printed final value if evaluation was successful, and any errors and warnings encountered.
It is frequently useful to regenerate the expected output.
To do that, rerun the failed test(s) with `_NIX_TEST_ACCEPT=1`.
For example:
```bash
_NIX_TEST_ACCEPT=1 meson test lang
```
This convention is shared with the [characterisation unit tests](#characterisation-testing-unit) too.
An interesting situation to document is the case when these tests are "overfitted".
The language tests are, again, an example of this.
The expected successful output of evaluation is supposed to be highly stable – we do not intend to make breaking changes to (the stable parts of) the Nix language.
However, the errors and warnings during evaluation (successful or not) are not stable in this way.
We are free to change how they are displayed at any time.
It may be surprising that we would test non-normative behavior like diagnostic outputs.
Diagnostic outputs are indeed not a stable interface, but they still are important to users.
By recording the expected output, the test suite guards against accidental changes, and ensure the *result* (not just the code that implements it) of the diagnostic code paths are under code review.
Regressions are caught, and improvements always show up in code review.
To ensure that characterisation testing doesn't make it harder to intentionally change these interfaces, there always must be an easy way to regenerate the expected output, as we do with `_NIX_TEST_ACCEPT=1`.
### Running functional tests on NixOS
We run the functional tests not just in the build, but also in VM tests.
This helps us ensure that Nix works correctly on NixOS, and environments that have similar characteristics that are hard to reproduce in a build environment.
These can be run with:
```shell
nix build .#hydraJobs.tests.functional_user
```
Generally, this build is sufficient, but in nightly or CI we also test the attributes `functional_root` and `functional_trusted`, in which the test suite is run with different levels of authorization.
## Integration tests
The integration tests are defined in the Nix flake under the `hydraJobs.tests` attribute.
These tests include everything that needs to interact with external services or run Nix in a non-trivial distributed setup.
Because these tests are expensive and require more than what the standard github-actions setup provides, they only run on the master branch (on <https://hydra.nixos.org/jobset/nix/master>).
You can run them manually with `nix build .#hydraJobs.tests.{testName}` or `nix-build -A hydraJobs.tests.{testName}`.
## Installer tests
After a one-time setup, the Nix repository's GitHub Actions continuous integration (CI) workflow can test the installer each time you push to a branch.
Creating a Cachix cache for your installer tests and adding its authorisation token to GitHub enables [two installer-specific jobs in the CI workflow](https://github.com/NixOS/nix/blob/88a45d6149c0e304f6eb2efcc2d7a4d0d569f8af/.github/workflows/ci.yml#L50-L91):
- The `installer` job generates installers for the platforms below and uploads them to your Cachix cache:
- `x86_64-linux`
- `armv6l-linux`
- `armv7l-linux`
- `x86_64-darwin`
- The `installer_test` job (which runs on `ubuntu-24.04` and `macos-14`) will try to install Nix with the cached installer and run a trivial Nix command.
### One-time setup
1. Have a GitHub account with a fork of the [Nix repository](https://github.com/NixOS/nix).
2. At cachix.org:
- Create or log in to an account.
- Create a Cachix cache using the format `<github-username>-nix-install-tests`.
- Navigate to the new cache > Settings > Auth Tokens.
- Generate a new Cachix auth token and copy the generated value.
3. At github.com:
- Navigate to your Nix fork > Settings > Secrets > Actions > New repository secret.
- Name the secret `CACHIX_AUTH_TOKEN`.
- Paste the copied value of the Cachix cache auth token.
## Working on documentation
### Using the CI-generated installer for manual testing
After the CI run completes, you can check the output to extract the installer URL:
1. Click into the detailed view of the CI run.
2. Click into any `installer_test` run (the URL you're here to extract will be the same in all of them).
3. Click into the `Run cachix/install-nix-action@v...` step and click the detail triangle next to the first log line (it will also be `Run cachix/install-nix-action@v...`)
4. Copy the value of `install_url`
5. To generate an install command, plug this `install_url` and your GitHub username into this template:
```console
curl -L <install_url> | sh -s -- --tarball-url-prefix https://<github-username>-nix-install-tests.cachix.org/serve
```
<!-- #### Manually generating test installers
There's obviously a manual way to do this, and it's still the only way for
platforms that lack GA runners.
I did do this back in Fall 2020 (before the GA approach encouraged here). I'll
sketch what I recall in case it encourages someone to fill in detail, but: I
didn't know what I was doing at the time and had to fumble/ask around a lot--
so I don't want to uphold any of it as "right". It may have been dumb or
the _hard_ way from the getgo. Fundamentals may have changed since.
Here's the build command I used to do this on and for x86_64-darwin:
nix build --out-link /tmp/foo ".#checks.x86_64-darwin.binaryTarball"
I used the stable out-link to make it easier to script the next steps:
link=$(readlink /tmp/foo)
cp $link/*-darwin.tar.xz ~/somewheres
I've lost the last steps and am just going from memory:
From here, I think I had to extract and modify the `install` script to point
it at this tarball (which I scped to my own site, but it might make more sense
to just share them locally). I extracted this script once and then just
search/replaced in it for each new build.
The installer now supports a `--tarball-url-prefix` flag which _may_ have
solved this need?
-->

BIN
doc/manual/source/favicon.png Normal file
View file

Binary file not shown.
Side by side

After

Width:  |  Height:  |  Size: 1.2 KiB

1
doc/manual/source/favicon.svg Normal file
View file

@ -0,0 +1 @@
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="587.11" height="516.604" viewBox="0 0 550.416 484.317"><defs><linearGradient id="a"><stop offset="0" style="stop-color:#699ad7;stop-opacity:1"/><stop offset=".243" style="stop-color:#7eb1dd;stop-opacity:1"/><stop offset="1" style="stop-color:#7ebae4;stop-opacity:1"/></linearGradient><linearGradient id="b"><stop offset="0" style="stop-color:#415e9a;stop-opacity:1"/><stop offset=".232" style="stop-color:#4a6baf;stop-opacity:1"/><stop offset="1" style="stop-color:#5277c3;stop-opacity:1"/></linearGradient><linearGradient xlink:href="#a" id="c" x1="200.597" x2="290.087" y1="351.411" y2="506.188" gradientTransform="translate(70.65 -1055.151)" gradientUnits="userSpaceOnUse"/><linearGradient xlink:href="#b" id="e" x1="-584.199" x2="-496.297" y1="782.336" y2="937.714" gradientTransform="translate(864.696 -1491.34)" gradientUnits="userSpaceOnUse"/></defs><g style="display:inline;opacity:1" transform="translate(-132.651 958.04)"><path id="d" d="m309.549-710.388 122.197 211.675-56.157.527-32.624-56.87-32.856 56.566-27.903-.011-14.29-24.69 46.81-80.49-33.23-57.826z" style="opacity:1;fill:url(#c);fill-opacity:1;fill-rule:evenodd;stroke:none;stroke-width:3;stroke-linecap:butt;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"/><use xlink:href="#d" width="100%" height="100%" transform="rotate(60 407.112 -715.787)"/><use xlink:href="#d" width="100%" height="100%" transform="rotate(-60 407.312 -715.7)"/><use xlink:href="#d" width="100%" height="100%" transform="rotate(180 407.419 -715.756)"/><path id="f" d="m309.549-710.388 122.197 211.675-56.157.527-32.624-56.87-32.856 56.566-27.903-.011-14.29-24.69 46.81-80.49-33.23-57.826z" style="color:#000;clip-rule:nonzero;display:inline;overflow:visible;visibility:visible;opacity:1;isolation:auto;mix-blend-mode:normal;color-interpolation:sRGB;color-interpolation-filters:linearRGB;solid-color:#000;solid-opacity:1;fill:url(#e);fill-opacity:1;fill-rule:evenodd;stroke:none;stroke-width:3;stroke-linecap:butt;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;color-rendering:auto;image-rendering:auto;shape-rendering:auto;text-rendering:auto;enable-background:accumulate"/><use xlink:href="#f" width="100%" height="100%" style="display:inline" transform="rotate(120 407.34 -716.084)"/><use xlink:href="#f" width="100%" height="100%" style="display:inline" transform="rotate(-120 407.288 -715.87)"/></g></svg>
Side by side

After

Width:  |  Height:  |  Size: 2.5 KiB

BIN
doc/manual/source/figures/user-environments.png Normal file
View file

Binary file not shown.
Side by side

After

Width:  |  Height:  |  Size: 83 KiB

BIN
doc/manual/source/figures/user-environments.sxd Normal file
View file

Binary file not shown.

364
doc/manual/source/glossary.md Normal file
View file

@ -0,0 +1,364 @@
# Glossary
- [content address]{#gloss-content-address}
A
[*content address*](https://en.wikipedia.org/wiki/Content-addressable_storage)
is a secure way to reference immutable data.
The reference is calculated directly from the content of the data being referenced, which means the reference is
[*tamper proof*](https://en.wikipedia.org/wiki/Tamperproofing)
--- variations of the data should always calculate to distinct content addresses.
For how Nix uses content addresses, see:
- [Content-Addressing File System Objects](@docroot@/store/file-system-object/content-address.md)
- [Content-Addressing Store Objects](@docroot@/store/store-object/content-address.md)
- [content-addressed derivation](#gloss-content-addressed-derivation)
Software Heritage's writing on [*Intrinsic and Extrinsic identifiers*](https://www.softwareheritage.org/2020/07/09/intrinsic-vs-extrinsic-identifiers) is also a good introduction to the value of content-addressing over other referencing schemes.
Besides content addressing, the Nix store also uses [input addressing](#gloss-input-addressed-store-object).
- [derivation]{#gloss-derivation}
A description of a build task. The result of a derivation is a
store object. Derivations declared in Nix expressions are specified
using the [`derivation` primitive](./language/derivations.md). These are
translated into low-level *store derivations* (implicitly by
`nix-build`, or explicitly by `nix-instantiate`).
[derivation]: #gloss-derivation
- [store derivation]{#gloss-store-derivation}
A [derivation] represented as a `.drv` file in the [store].
It has a [store path], like any [store object].
It is the [instantiated][instantiate] form of a derivation.
Example: `/nix/store/g946hcz4c8mdvq2g8vxx42z51qb71rvp-git-2.38.1.drv`
See [`nix derivation show`](./command-ref/new-cli/nix3-derivation-show.md) (experimental) for displaying the contents of store derivations.
[store derivation]: #gloss-store-derivation
- [instantiate]{#gloss-instantiate}, instantiation
Save an evaluated [derivation] as a [store derivation] in the Nix [store].
See [`nix-instantiate`](./command-ref/nix-instantiate.md), which produces a store derivation from a Nix expression that evaluates to a derivation.
[instantiate]: #gloss-instantiate
- [realise]{#gloss-realise}, realisation
Ensure a [store path] is [valid][validity].
This can be achieved by:
- Fetching a pre-built [store object] from a [substituter]
- Running the [`builder`](@docroot@/language/derivations.md#attr-builder) executable as specified in the corresponding [derivation]
- Delegating to a [remote machine](@docroot@/command-ref/conf-file.md#conf-builders) and retrieving the outputs
<!-- TODO: link [running] to build process page, #8888 -->
See [`nix-store --realise`](@docroot@/command-ref/nix-store/realise.md) for a detailed description of the algorithm.
See also [`nix-build`](./command-ref/nix-build.md) and [`nix build`](./command-ref/new-cli/nix3-build.md) (experimental).
[realise]: #gloss-realise
- [content-addressed derivation]{#gloss-content-addressed-derivation}
A derivation which has the
[`__contentAddressed`](./language/advanced-attributes.md#adv-attr-__contentAddressed)
attribute set to `true`.
- [fixed-output derivation]{#gloss-fixed-output-derivation} (FOD)
A [derivation] where a cryptographic hash of the [output] is determined in advance using the [`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute, and where the [`builder`](@docroot@/language/derivations.md#attr-builder) executable has access to the network.
- [store]{#gloss-store}
A collection of [store objects][store object], with operations to manipulate that collection.
See [Nix Store](./store/index.md) for details.
There are many types of stores, see [Store Types](./store/types/index.md) for details.
[store]: #gloss-store
- [binary cache]{#gloss-binary-cache}
A *binary cache* is a Nix store which uses a different format: its
metadata and signatures are kept in `.narinfo` files rather than in a
[Nix database]. This different format simplifies serving store objects
over the network, but cannot host builds. Examples of binary caches
include S3 buckets and the [NixOS binary cache](https://cache.nixos.org).
- [store path]{#gloss-store-path}
The location of a [store object] in the file system, i.e., an immediate child of the Nix store directory.
> **Example**
>
> `/nix/store/a040m110amc4h71lds2jmr8qrkj2jhxd-git-2.38.1`
See [Store Path](@docroot@/store/store-path.md) for details.
[store path]: #gloss-store-path
- [file system object]{#gloss-file-system-object}
The Nix data model for representing simplified file system data.
See [File System Object](@docroot@/store/file-system-object.md) for details.
[file system object]: #gloss-file-system-object
- [store object]{#gloss-store-object}
Part of the contents of a [store].
A store object consists of a [file system object], [references][reference] to other store objects, and other metadata.
It can be referred to by a [store path].
See [Store Object](@docroot@/store/store-object.md) for details.
[store object]: #gloss-store-object
- [IFD]{#gloss-ifd}
[Import From Derivation](./language/import-from-derivation.md)
- [input-addressed store object]{#gloss-input-addressed-store-object}
A store object produced by building a
non-[content-addressed](#gloss-content-addressed-derivation),
non-[fixed-output](#gloss-fixed-output-derivation)
derivation.
- [content-addressed store object]{#gloss-content-addressed-store-object}
A [store object] which is [content-addressed](#gloss-content-address),
i.e. whose [store path] is determined by its contents.
This includes derivations, the outputs of [content-addressed derivations](#gloss-content-addressed-derivation), and the outputs of [fixed-output derivations](#gloss-fixed-output-derivation).
See [Content-Addressing Store Objects](@docroot@/store/store-object/content-address.md) for details.
- [substitute]{#gloss-substitute}
A substitute is a command invocation stored in the [Nix database] that
describes how to build a store object, bypassing the normal build
mechanism (i.e., derivations). Typically, the substitute builds the
store object by downloading a pre-built version of the store object
from some server.
- [substituter]{#gloss-substituter}
An additional [store]{#gloss-store} from which Nix can obtain store objects instead of building them.
Often the substituter is a [binary cache](#gloss-binary-cache), but any store can serve as substituter.
See the [`substituters` configuration option](./command-ref/conf-file.md#conf-substituters) for details.
[substituter]: #gloss-substituter
- [purity]{#gloss-purity}
The assumption that equal Nix derivations when run always produce
the same output. This cannot be guaranteed in general (e.g., a
builder can rely on external inputs such as the network or the
system time) but the Nix model assumes it.
- [impure derivation]{#gloss-impure-derivation}
[An experimental feature](#@docroot@/development/experimental-features.md#xp-feature-impure-derivations) that allows derivations to be explicitly marked as impure,
so that they are always rebuilt, and their outputs not reused by subsequent calls to realise them.
- [Nix database]{#gloss-nix-database}
An SQlite database to track [reference]s between [store object]s.
This is an implementation detail of the [local store].
Default location: `/nix/var/nix/db`.
[Nix database]: #gloss-nix-database
- [Nix expression]{#gloss-nix-expression}
A syntactically valid use of the [Nix language].
> **Example**
>
> The contents of a `.nix` file form a Nix expression.
Nix expressions specify [derivations][derivation], which are [instantiated][instantiate] into the Nix store as [store derivations][store derivation].
These derivations can then be [realised][realise] to produce [outputs][output].
> **Example**
>
> Building and deploying software using Nix entails writing Nix expressions as a high-level description of packages and compositions thereof.
- [reference]{#gloss-reference}
A [store object] `O` is said to have a *reference* to a store object `P` if a [store path] to `P` appears in the contents of `O`.
Store objects can refer to both other store objects and themselves.
References from a store object to itself are called *self-references*.
References other than a self-reference must not form a cycle.
[reference]: #gloss-reference
- [reachable]{#gloss-reachable}
A store path `Q` is reachable from another store path `P` if `Q`
is in the *closure* of the *references* relation.
- [closure]{#gloss-closure}
The closure of a store path is the set of store paths that are
directly or indirectly “reachable” from that store path; that is,
it’s the closure of the path under the *references* relation. For
a package, the closure of its derivation is equivalent to the
build-time dependencies, while the closure of its output path is
equivalent to its runtime dependencies. For correct deployment it
is necessary to deploy whole closures, since otherwise at runtime
files could be missing. The command `nix-store --query --requisites ` prints out
closures of store paths.
As an example, if the [store object] at path `P` contains a [reference]
to a store object at path `Q`, then `Q` is in the closure of `P`. Further, if `Q`
references `R` then `R` is also in the closure of `P`.
[closure]: #gloss-closure
- [output]{#gloss-output}
A [store object] produced by a [derivation].
See [the `outputs` argument to the `derivation` function](@docroot@/language/derivations.md#attr-outputs) for details.
[output]: #gloss-output
- [output path]{#gloss-output-path}
The [store path] to the [output] of a [derivation].
[output path]: #gloss-output-path
- [output closure]{#gloss-output-closure}\
The [closure] of an [output path]. It only contains what is [reachable] from the output.
- [deriving path]{#gloss-deriving-path}
Deriving paths are a way to refer to [store objects][store object] that ar not yet [realised][realise].
This is necessary because, in general and particularly for [content-addressed derivations][content-addressed derivation], the [output path] of an [output] is not known in advance.
There are two forms:
- *constant*: just a [store path]
It can be made [valid][validity] by copying it into the store: from the evaluator, command line interface or another store.
- *output*: a pair of a [store path] to a [derivation] and an [output] name.
- [deriver]{#gloss-deriver}
The [store derivation] that produced an [output path].
The deriver for an output path can be queried with the `--deriver` option to
[`nix-store --query`](@docroot@/command-ref/nix-store/query.md).
- [validity]{#gloss-validity}
A store path is valid if all [store object]s in its [closure] can be read from the [store].
For a [local store], this means:
- The store path leads to an existing [store object] in that [store].
- The store path is listed in the [Nix database] as being valid.
- All paths in the store path's [closure] are valid.
[validity]: #gloss-validity
[local store]: @docroot@/store/types/local-store.md
- [user environment]{#gloss-user-env}
An automatically generated store object that consists of a set of
symlinks to “active” applications, i.e., other store paths. These
are generated automatically by
[`nix-env`](./command-ref/nix-env.md). See *profiles*.
- [profile]{#gloss-profile}
A symlink to the current *user environment* of a user, e.g.,
`/nix/var/nix/profiles/default`.
- [installable]{#gloss-installable}
Something that can be realised in the Nix store.
See [installables](./command-ref/new-cli/nix.md#installables) for [`nix` commands](./command-ref/new-cli/nix.md) (experimental) for details.
- [Nix Archive (NAR)]{#gloss-nar}
A *N*ix *AR*chive. This is a serialisation of a path in the Nix
store. It can contain regular files, directories and symbolic
links. NARs are generated and unpacked using `nix-store --dump`
and `nix-store --restore`.
See [Nix Archive](store/file-system-object/content-address.html#serial-nix-archive) for details.
- [`∅`]{#gloss-emtpy-set}
The empty set symbol. In the context of profile history, this denotes a package is not present in a particular version of the profile.
- [`ε`]{#gloss-epsilon}
The epsilon symbol. In the context of a package, this means the version is empty. More precisely, the derivation does not have a version attribute.
- [package]{#package}
1. A software package; a collection of files and other data.
2. A [package attribute set].
- [package attribute set]{#package-attribute-set}
An [attribute set](@docroot@/language/types.md#attribute-set) containing the attribute `type = "derivation";` (derivation for historical reasons), as well as other attributes, such as
- attributes that refer to the files of a [package], typically in the form of [derivation outputs](#output),
- attributes that declare something about how the package is supposed to be installed or used,
- other metadata or arbitrary attributes.
[package attribute set]: #package-attribute-set
- [string interpolation]{#gloss-string-interpolation}
Expanding expressions enclosed in `${ }` within a [string], [path], or [attribute name].
See [String interpolation](./language/string-interpolation.md) for details.
[string]: ./language/types.md#type-string
[path]: ./language/types.md#type-path
[attribute name]: ./language/types.md#attribute-set
- [base directory]{#gloss-base-directory}
The location from which relative paths are resolved.
- For expressions in a file, the base directory is the directory containing that file.
This is analogous to the directory of a [base URL](https://datatracker.ietf.org/doc/html/rfc1808#section-3.3).
<!-- which is sufficient for resolving non-empty URLs -->
<!--
The wording here may look awkward, but it's for these reasons:
* "with --expr": it's a flag, and not an option with an accompanying value
* "written in": the expression itself must be written as an argument,
whereas the more natural "passed as an argument" allows an interpretation
where the expression could be passed by file name.
-->
- For expressions written in command line arguments with [`--expr`](@docroot@/command-ref/opt-common.html#opt-expr), the base directory is the current working directory.
[base directory]: #gloss-base-directory
- [experimental feature]{#gloss-experimental-feature}
Not yet stabilized functionality guarded by named experimental feature flags.
These flags are enabled or disabled with the [`experimental-features`](./command-ref/conf-file.html#conf-experimental-features) setting.
See the contribution guide on the [purpose and lifecycle of experimental feaures](@docroot@/development/experimental-features.md).
[Nix language]: ./language/index.md

26
doc/manual/source/installation/building-source.md Normal file
View file

@ -0,0 +1,26 @@
# Building Nix from Source
Nix is built with [Meson](https://mesonbuild.com/).
It is broken up into multiple Meson packages, which are optionally combined in a single project using Meson's [subprojects](https://mesonbuild.com/Subprojects.html) feature.
There are no mandatory extra steps to the building process:
generic Meson installation instructions like [this](https://mesonbuild.com/Quick-guide.html#using-meson-as-a-distro-packager) should work.
The installation path can be specified by passing the `-Dprefix=prefix`
to `configure`. The default installation directory is `/usr/local`. You
can change this to any location you like. You must have write permission
to the *prefix* path.
Nix keeps its *store* (the place where packages are stored) in
`/nix/store` by default. This can be changed using
`-Dstore-dir=path`.
> **Warning**
>
> It is best *not* to change the Nix store from its default, since doing
> so makes it impossible to use pre-built binaries from the standard
> Nixpkgs channels — that is, all packages will need to be built from
> source.
Nix keeps state (such as its database and log files) in `/nix/var` by
default. This can be changed using `-Dlocalstatedir=path`.

62
doc/manual/source/installation/env-variables.md Normal file
View file

@ -0,0 +1,62 @@
# Environment Variables
To use Nix, some environment variables should be set. In particular,
`PATH` should contain the directories `prefix/bin` and
`~/.nix-profile/bin`. The first directory contains the Nix tools
themselves, while `~/.nix-profile` is a symbolic link to the current
*user environment* (an automatically generated package consisting of
symlinks to installed packages). The simplest way to set the required
environment variables is to include the file
`prefix/etc/profile.d/nix.sh` in your `~/.profile` (or similar), like
this:
```bash
source prefix/etc/profile.d/nix.sh
```
# `NIX_SSL_CERT_FILE`
If you need to specify a custom certificate bundle to account for an
HTTPS-intercepting man in the middle proxy, you must specify the path to
the certificate bundle in the environment variable `NIX_SSL_CERT_FILE`.
If you don't specify a `NIX_SSL_CERT_FILE` manually, Nix will install
and use its own certificate bundle.
Set the environment variable and install Nix
```console
$ export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
$ curl -L https://nixos.org/nix/install | sh
```
In the shell profile and rc files (for example, `/etc/bashrc`,
`/etc/zshrc`), add the following line:
```bash
export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
```
> **Note**
>
> You must not add the export and then do the install, as the Nix
> installer will detect the presence of Nix configuration, and abort.
If you use the Nix daemon, you should also add the following to
`/etc/nix/nix.conf`:
```
ssl-cert-file = /etc/ssl/my-certificate-bundle.crt
```
## Proxy Environment Variables
The Nix installer has special handling for these proxy-related
environment variables: `http_proxy`, `https_proxy`, `ftp_proxy`,
`all_proxy`, `no_proxy`, `HTTP_PROXY`, `HTTPS_PROXY`, `FTP_PROXY`,
`ALL_PROXY`, `NO_PROXY`.
If any of these variables are set when running the Nix installer, then
the installer will create an override file at
`/etc/systemd/system/nix-daemon.service.d/override.conf` so `nix-daemon`
will use them.

46
doc/manual/source/installation/index.md Normal file
View file

@ -0,0 +1,46 @@
# Installation
This section describes how to install and configure Nix for first-time use.
The current recommended option on Linux and MacOS is [multi-user](#multi-user).
## Multi-user
This installation offers better sharing, improved isolation, and more security
over a single user installation.
This option requires either:
* Linux running systemd, with SELinux disabled
* MacOS
> **Updating to macOS 15 Sequoia**
>
> If you recently updated to macOS 15 Sequoia and are getting
> ```console
> error: the user '_nixbld1' in the group 'nixbld' does not exist
> ```
> when running Nix commands, refer to GitHub issue [NixOS/nix#10892](https://github.com/NixOS/nix/issues/10892) for instructions to fix your installation without reinstalling.
```console
$ curl -L https://nixos.org/nix/install | sh -s -- --daemon
```
## Single-user
> Single-user is not supported on Mac.
This installation has less requirements than the multi-user install, however it
cannot offer equivalent sharing, isolation, or security.
This option is suitable for systems without systemd.
```console
$ curl -L https://nixos.org/nix/install | sh -s -- --no-daemon
```
## Distributions
The Nix community maintains installers for several distributions.
They can be found in the [`nix-community/nix-installers`](https://github.com/nix-community/nix-installers) repository.

158
doc/manual/source/installation/installing-binary.md Normal file
View file

@ -0,0 +1,158 @@
# Installing a Binary Distribution
> **Updating to macOS 15 Sequoia**
>
> If you recently updated to macOS 15 Sequoia and are getting
> ```console
> error: the user '_nixbld1' in the group 'nixbld' does not exist
> ```
> when running Nix commands, refer to GitHub issue [NixOS/nix#10892](https://github.com/NixOS/nix/issues/10892) for instructions to fix your installation without reinstalling.
To install the latest version Nix, run the following command:
```console
$ curl -L https://nixos.org/nix/install | sh
```
This performs the default type of installation for your platform:
- [Multi-user](#multi-user-installation):
- Linux with systemd and without SELinux
- macOS
- [Single-user](#single-user-installation):
- Linux without systemd
- Linux with SELinux
We recommend the multi-user installation if it supports your platform and you can authenticate with `sudo`.
The installer can configured with various command line arguments and environment variables.
To show available command line flags:
```console
$ curl -L https://nixos.org/nix/install | sh -s -- --help
```
To check what it does and how it can be customised further, [download and edit the second-stage installation script](#installing-from-a-binary-tarball).
# Installing a pinned Nix version from a URL
Version-specific installation URLs for all Nix versions since 1.11.16 can be found at [releases.nixos.org](https://releases.nixos.org/?prefix=nix/).
The directory for each version contains the corresponding SHA-256 hash.
All installation scripts are invoked the same way:
```console
$ export VERSION=2.19.2
$ curl -L https://releases.nixos.org/nix/nix-$VERSION/install | sh
```
# Multi User Installation
The multi-user Nix installation creates system users and a system service for the Nix daemon.
Supported systems:
- Linux running systemd, with SELinux disabled
- macOS
To explicitly instruct the installer to perform a multi-user installation on your system:
```console
$ bash <(curl -L https://nixos.org/nix/install) --daemon
```
You can run this under your usual user account or `root`.
The script will invoke `sudo` as needed.
# Single User Installation
To explicitly select a single-user installation on your system:
```console
$ bash <(curl -L https://nixos.org/nix/install) --no-daemon
```
In a single-user installation, `/nix` is owned by the invoking user.
The script will invoke `sudo` to create `/nix` if it doesn’t already exist.
If you don’t have `sudo`, manually create `/nix` as `root`:
```console
$ su root
# mkdir /nix
# chown alice /nix
```
# Installing from a binary tarball
You can also download a binary tarball that contains Nix and all its dependencies:
- Choose a [version](https://releases.nixos.org/?prefix=nix/) and [system type](../development/building.md#platforms)
- Download and unpack the tarball
- Run the installer
> **Example**
>
> ```console
> $ pushd $(mktemp -d)
> $ export VERSION=2.19.2
> $ export SYSTEM=x86_64-linux
> $ curl -LO https://releases.nixos.org/nix/nix-$VERSION/nix-$VERSION-$SYSTEM.tar.xz
> $ tar xfj nix-$VERSION-$SYSTEM.tar.xz
> $ cd nix-$VERSION-$SYSTEM
> $ ./install
> $ popd
> ```
The installer can be customised with the environment variables declared in the file named `install-multi-user`.
## Native packages for Linux distributions
The Nix community maintains installers for some Linux distributions in their native packaging format(https://nix-community.github.io/nix-installers/).
# macOS Installation
<!-- anchors to catch existing links -->
[]{#sect-macos-installation-change-store-prefix}[]{#sect-macos-installation-encrypted-volume}[]{#sect-macos-installation-symlink}[]{#sect-macos-installation-recommended-notes}
We believe we have ironed out how to cleanly support the read-only root file system
on modern macOS. New installs will do this automatically.
This section previously detailed the situation, options, and trade-offs,
but it now only outlines what the installer does. You don't need to know
this to run the installer, but it may help if you run into trouble:
- create a new APFS volume for your Nix store
- update `/etc/synthetic.conf` to direct macOS to create a "synthetic"
empty root directory to mount your volume
- specify mount options for the volume in `/etc/fstab`
- `rw`: read-write
- `noauto`: prevent the system from auto-mounting the volume (so the
LaunchDaemon mentioned below can control mounting it, and to avoid
masking problems with that mounting service).
- `nobrowse`: prevent the Nix Store volume from showing up on your
desktop; also keeps Spotlight from spending resources to index
this volume
<!-- TODO:
- `suid`: honor setuid? surely not? ...
- `owners`: honor file ownership on the volume
For now I'll avoid pretending to understand suid/owners more
than I do. There've been some vague reports of file-ownership
and permission issues, particularly in cloud/VM/headless setups.
My pet theory is that this has something to do with these setups
not having a token that gets delegated to initial/admin accounts
on macOS. See scripts/create-darwin-volume.sh for a little more.
In any case, by Dec 4 2021, it _seems_ like some combination of
suid, owners, and calling diskutil enableOwnership have stopped
new reports from coming in. But I hesitate to celebrate because we
haven't really named and catalogued the behavior, understood what
we're fixing, and validated that all 3 components are essential.
-->
- if you have FileVault enabled
- generate an encryption password
- put it in your system Keychain
- use it to encrypt the volume
- create a system LaunchDaemon to mount this volume early enough in the
boot process to avoid problems loading or restoring any programs that
need access to your Nix store

77
doc/manual/source/installation/installing-docker.md Normal file
View file

@ -0,0 +1,77 @@
# Using Nix within Docker
To run the latest stable release of Nix with Docker run the following command:
```console
$ docker run -ti ghcr.io/nixos/nix
Unable to find image 'ghcr.io/nixos/nix:latest' locally
latest: Pulling from ghcr.io/nixos/nix
5843afab3874: Pull complete
b52bf13f109c: Pull complete
1e2415612aa3: Pull complete
Digest: sha256:27f6e7f60227e959ee7ece361f75d4844a40e1cc6878b6868fe30140420031ff
Status: Downloaded newer image for ghcr.io/nixos/nix:latest
35ca4ada6e96:/# nix --version
nix (Nix) 2.3.12
35ca4ada6e96:/# exit
```
# What is included in Nix's Docker image?
The official Docker image is created using `pkgs.dockerTools.buildLayeredImage`
(and not with `Dockerfile` as it is usual with Docker images). You can still
base your custom Docker image on it as you would do with any other Docker
image.
The Docker image is also not based on any other image and includes minimal set
of runtime dependencies that are required to use Nix:
- pkgs.nix
- pkgs.bashInteractive
- pkgs.coreutils-full
- pkgs.gnutar
- pkgs.gzip
- pkgs.gnugrep
- pkgs.which
- pkgs.curl
- pkgs.less
- pkgs.wget
- pkgs.man
- pkgs.cacert.out
- pkgs.findutils
# Docker image with the latest development version of Nix
To get the latest image that was built by [Hydra](https://hydra.nixos.org) run
the following command:
```console
$ curl -L https://hydra.nixos.org/job/nix/master/dockerImage.x86_64-linux/latest/download/1 | docker load
$ docker run -ti nix:2.5pre20211105
```
You can also build a Docker image from source yourself:
```console
$ nix build ./\#hydraJobs.dockerImage.x86_64-linux
$ docker load -i ./result/image.tar.gz
$ docker run -ti nix:2.5pre20211105
```
# Docker image with non-root Nix
If you would like to run Nix in a container under a user other than `root`,
you can build an image with a non-root single-user installation of Nix
by specifying the `uid`, `gid`, `uname`, and `gname` arguments to `docker.nix`:
```console
$ nix build --file docker.nix \
--arg uid 1000 \
--arg gid 1000 \
--argstr uname user \
--argstr gname user \
--argstr name nix-user \
--out-link nix-user.tar.gz
$ docker load -i nix-user.tar.gz
$ docker run -ti nix-user
```

4
doc/manual/source/installation/installing-source.md Normal file
View file

@ -0,0 +1,4 @@
# Installing Nix from Source
If no binary package is available or if you want to hack on Nix, you
can build Nix from its Git repository.

77
doc/manual/source/installation/multi-user.md Normal file
View file

@ -0,0 +1,77 @@
# Multi-User Mode
To allow a Nix store to be shared safely among multiple users, it is
important that users are not able to run builders that modify the Nix
store or database in arbitrary ways, or that interfere with builds
started by other users. If they could do so, they could install a Trojan
horse in some package and compromise the accounts of other users.
To prevent this, the Nix store and database are owned by some privileged
user (usually `root`) and builders are executed under special user
accounts (usually named `nixbld1`, `nixbld2`, etc.). When a unprivileged
user runs a Nix command, actions that operate on the Nix store (such as
builds) are forwarded to a *Nix daemon* running under the owner of the
Nix store/database that performs the operation.
> **Note**
>
> Multi-user mode has one important limitation: only root and a set of
> trusted users specified in `nix.conf` can specify arbitrary binary
> caches. So while unprivileged users may install packages from
> arbitrary Nix expressions, they may not get pre-built binaries.
## Setting up the build users
The *build users* are the special UIDs under which builds are performed.
They should all be members of the *build users group* `nixbld`. This
group should have no other members. The build users should not be
members of any other group. On Linux, you can create the group and users
as follows:
```console
$ groupadd -r nixbld
$ for n in $(seq 1 10); do useradd -c "Nix build user $n" \
-d /var/empty -g nixbld -G nixbld -M -N -r -s "$(which nologin)" \
nixbld$n; done
```
This creates 10 build users. There can never be more concurrent builds
than the number of build users, so you may want to increase this if you
expect to do many builds at the same time.
## Running the daemon
The [Nix daemon](../command-ref/nix-daemon.md) should be started as
follows (as `root`):
```console
$ nix-daemon
```
You’ll want to put that line somewhere in your system’s boot scripts.
To let unprivileged users use the daemon, they should set the
[`NIX_REMOTE` environment variable](../command-ref/env-common.md) to
`daemon`. So you should put a line like
```console
export NIX_REMOTE=daemon
```
into the users’ login scripts.
## Restricting access
To limit which users can perform Nix operations, you can use the
permissions on the directory `/nix/var/nix/daemon-socket`. For instance,
if you want to restrict the use of Nix to the members of a group called
`nix-users`, do
```console
$ chgrp nix-users /nix/var/nix/daemon-socket
$ chmod ug=rwx,o= /nix/var/nix/daemon-socket
```
This way, users who are not in the `nix-users` group cannot connect to
the Unix domain socket `/nix/var/nix/daemon-socket/socket`, so they
cannot perform Nix operations.

15
doc/manual/source/installation/nix-security.md Normal file
View file

@ -0,0 +1,15 @@
# Security
Nix has two basic security models. First, it can be used in “single-user
mode”, which is similar to what most other package management tools do:
there is a single user (typically root) who performs all package
management operations. All other users can then use the installed
packages, but they cannot perform package management operations
themselves.
Alternatively, you can configure Nix in “multi-user mode”. In this
model, all users can perform package management operations — for
instance, every user can install software without requiring root
privileges. Nix ensures that this is secure. For instance, it’s not
possible for one user to overwrite a package used by another user with a
Trojan horse.

13
doc/manual/source/installation/obtaining-source.md Normal file
View file

@ -0,0 +1,13 @@
# Obtaining the Source
The most recent sources of Nix can be obtained from its [Git
repository](https://github.com/NixOS/nix). For example, the following
command will check out the latest revision into a directory called
`nix`:
```console
$ git clone https://github.com/NixOS/nix
```
Likewise, specific releases can be obtained from the
[tags](https://github.com/NixOS/nix/tags) of the repository.

80
doc/manual/source/installation/prerequisites-source.md Normal file
View file

@ -0,0 +1,80 @@
# Prerequisites
- GNU Autoconf (<https://www.gnu.org/software/autoconf/>) and the
autoconf-archive macro collection
(<https://www.gnu.org/software/autoconf-archive/>). These are
needed to run the bootstrap script.
- GNU Make.
- Bash Shell. The `./configure` script relies on bashisms, so Bash is
required.
- A version of GCC or Clang that supports C++20.
- `pkg-config` to locate dependencies. If your distribution does not
provide it, you can get it from
<http://www.freedesktop.org/wiki/Software/pkg-config>.
- The OpenSSL library to calculate cryptographic hashes. If your
distribution does not provide it, you can get it from
<https://www.openssl.org>.
- The `libbrotlienc` and `libbrotlidec` libraries to provide
implementation of the Brotli compression algorithm. They are
available for download from the official repository
<https://github.com/google/brotli>.
- cURL and its library. If your distribution does not provide it, you
can get it from <https://curl.haxx.se/>.
- The SQLite embedded database library, version 3.6.19 or higher. If
your distribution does not provide it, please install it from
<http://www.sqlite.org/>.
- The [Boehm garbage collector (`bdw-gc`)](http://www.hboehm.info/gc/) to reduce
the evaluator’s memory consumption (optional).
To enable it, install
`pkgconfig` and the Boehm garbage collector, and pass the flag
`--enable-gc` to `configure`.
- The `boost` library of version 1.66.0 or higher. It can be obtained
from the official web site <https://www.boost.org/>.
- The `editline` library of version 1.14.0 or higher. It can be
obtained from the its repository
<https://github.com/troglobit/editline>.
- The `libsodium` library for verifying cryptographic signatures
of contents fetched from binary caches.
It can be obtained from the official web site
<https://libsodium.org>.
- Recent versions of Bison and Flex to build the parser. (This is
because Nix needs GLR support in Bison and reentrancy support in
Flex.) For Bison, you need version 2.6, which can be obtained from
the [GNU FTP server](ftp://alpha.gnu.org/pub/gnu/bison). For Flex,
you need version 2.5.35, which is available on
[SourceForge](http://lex.sourceforge.net/). Slightly older versions
may also work, but ancient versions like the ubiquitous 2.5.4a
won't.
- The `libseccomp` is used to provide syscall filtering on Linux. This
is an optional dependency and can be disabled passing a
`--disable-seccomp-sandboxing` option to the `configure` script (Not
recommended unless your system doesn't support `libseccomp`). To get
the library, visit <https://github.com/seccomp/libseccomp>.
- On 64-bit x86 machines only, `libcpuid` library
is used to determine which microarchitecture levels are supported
(e.g., as whether to have `x86_64-v2-linux` among additional system types).
The library is available from its homepage
<http://libcpuid.sourceforge.net>.
This is an optional dependency and can be disabled
by providing a `--disable-cpuid` to the `configure` script.
- Unless `./configure --disable-unit-tests` is specified, GoogleTest (GTest) and
RapidCheck are required, which are available at
<https://google.github.io/googletest/> and
<https://github.com/emil-e/rapidcheck> respectively.

9
doc/manual/source/installation/single-user.md Normal file
View file

@ -0,0 +1,9 @@
# Single-User Mode
In single-user mode, all Nix operations that access the database in
`prefix/var/nix/db` or modify the Nix store in `prefix/store` must be
performed under the user ID that owns those directories. This is
typically root. (If you install from RPM packages, that’s in fact the
default ownership.) However, on single-user machines, it is often
convenient to `chown` those directories to your normal user account so
that you don’t have to `su` to root all the time.

7
doc/manual/source/installation/supported-platforms.md Normal file
View file

@ -0,0 +1,7 @@
# Supported Platforms
Nix is currently supported on the following platforms:
- Linux (i686, x86\_64, aarch64).
- macOS (x86\_64, aarch64).

165
doc/manual/source/installation/uninstall.md Normal file
View file

@ -0,0 +1,165 @@
# Uninstalling Nix
## Multi User
Removing a [multi-user installation](./installing-binary.md#multi-user-installation) depends on the operating system.
### Linux
If you are on Linux with systemd:
1. Remove the Nix daemon service:
```console
sudo systemctl stop nix-daemon.service
sudo systemctl disable nix-daemon.socket nix-daemon.service
sudo systemctl daemon-reload
```
Remove files created by Nix:
```console
sudo rm -rf /etc/nix /etc/profile.d/nix.sh /etc/tmpfiles.d/nix-daemon.conf /nix ~root/.nix-channels ~root/.nix-defexpr ~root/.nix-profile ~root/.cache/nix
```
Remove build users and their group:
```console
for i in $(seq 1 32); do
sudo userdel nixbld$i
done
sudo groupdel nixbld
```
There may also be references to Nix in
- `/etc/bash.bashrc`
- `/etc/bashrc`
- `/etc/profile`
- `/etc/zsh/zshrc`
- `/etc/zshrc`
which you may remove.
### macOS
> **Updating to macOS 15 Sequoia**
>
> If you recently updated to macOS 15 Sequoia and are getting
> ```console
> error: the user '_nixbld1' in the group 'nixbld' does not exist
> ```
> when running Nix commands, refer to GitHub issue [NixOS/nix#10892](https://github.com/NixOS/nix/issues/10892) for instructions to fix your installation without reinstalling.
1. If system-wide shell initialisation files haven't been altered since installing Nix, use the backups made by the installer:
```console
sudo mv /etc/zshrc.backup-before-nix /etc/zshrc
sudo mv /etc/bashrc.backup-before-nix /etc/bashrc
sudo mv /etc/bash.bashrc.backup-before-nix /etc/bash.bashrc
```
Otherwise, edit `/etc/zshrc`, `/etc/bashrc`, and `/etc/bash.bashrc` to remove the lines sourcing `nix-daemon.sh`, which should look like this:
```bash
# Nix
if [ -e '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh' ]; then
. '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh'
fi
# End Nix
```
2. Stop and remove the Nix daemon services:
```console
sudo launchctl unload /Library/LaunchDaemons/org.nixos.nix-daemon.plist
sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist
sudo launchctl unload /Library/LaunchDaemons/org.nixos.darwin-store.plist
sudo rm /Library/LaunchDaemons/org.nixos.darwin-store.plist
```
This stops the Nix daemon and prevents it from being started next time you boot the system.
3. Remove the `nixbld` group and the `_nixbuildN` users:
```console
sudo dscl . -delete /Groups/nixbld
for u in $(sudo dscl . -list /Users | grep _nixbld); do sudo dscl . -delete /Users/$u; done
```
This will remove all the build users that no longer serve a purpose.
4. Edit fstab using `sudo vifs` to remove the line mounting the Nix Store volume on `/nix`, which looks like
```
UUID=<uuid> /nix apfs rw,noauto,nobrowse,suid,owners
```
or
```
LABEL=Nix\040Store /nix apfs rw,nobrowse
```
by setting the cursor on the respective line using the arrow keys, and pressing `dd`, and then `:wq` to save the file.
This will prevent automatic mounting of the Nix Store volume.
5. Edit `/etc/synthetic.conf` to remove the `nix` line.
If this is the only line in the file you can remove it entirely:
```bash
if [ -f /etc/synthetic.conf ]; then
if [ "$(cat /etc/synthetic.conf)" = "nix" ]; then
sudo rm /etc/synthetic.conf
else
sudo vi /etc/synthetic.conf
fi
fi
```
This will prevent the creation of the empty `/nix` directory.
6. Remove the files Nix added to your system, except for the store:
```console
sudo rm -rf /etc/nix /var/root/.nix-profile /var/root/.nix-defexpr /var/root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
```
7. Remove the Nix Store volume:
```console
sudo diskutil apfs deleteVolume /nix
```
This will remove the Nix Store volume and everything that was added to the store.
If the output indicates that the command couldn't remove the volume, you should make sure you don't have an _unmounted_ Nix Store volume.
Look for a "Nix Store" volume in the output of the following command:
```console
diskutil list
```
If you _do_ find a "Nix Store" volume, delete it by running `diskutil apfs deleteVolume` with the store volume's `diskXsY` identifier.
If you get an error that the volume is in use by the kernel, reboot and immediately delete the volume before starting any other process.
> **Note**
>
> After you complete the steps here, you will still have an empty `/nix` directory.
> This is an expected sign of a successful uninstall.
> The empty `/nix` directory will disappear the next time you reboot.
>
> You do not have to reboot to finish uninstalling Nix.
> The uninstall is complete.
> macOS (Catalina+) directly controls root directories, and its read-only root will prevent you from manually deleting the empty `/nix` mountpoint.
## Single User
To remove a [single-user installation](./installing-binary.md#single-user-installation) of Nix, run:
```console
rm -rf /nix ~/.nix-channels ~/.nix-defexpr ~/.nix-profile
```
You might also want to manually remove references to Nix from your `~/.profile`.

40
doc/manual/source/installation/upgrading.md Normal file
View file

@ -0,0 +1,40 @@
# Upgrading Nix
> **Note**
>
> These upgrade instructions apply where Nix was installed following the [installation instructions in this manual](./index.md).
Check which Nix version will be installed, for example from one of the [release channels](http://channels.nixos.org/) such as `nixpkgs-unstable`:
```console
$ nix-shell -p nix -I nixpkgs=channel:nixpkgs-unstable --run "nix --version"
nix (Nix) 2.18.1
```
> **Warning**
>
> Writing to the [local store](@docroot@/store/types/local-store.md) with a newer version of Nix, for example by building derivations with [`nix-build`](@docroot@/command-ref/nix-build.md) or [`nix-store --realise`](@docroot@/command-ref/nix-store/realise.md), may change the database schema!
> Reverting to an older version of Nix may therefore require purging the store database before it can be used.
## Linux multi-user
```console
$ sudo su
# nix-env --install --file '<nixpkgs>' --attr nix cacert -I nixpkgs=channel:nixpkgs-unstable
# systemctl daemon-reload
# systemctl restart nix-daemon
```
## macOS multi-user
```console
$ sudo nix-env --install --file '<nixpkgs>' --attr nix cacert -I nixpkgs=channel:nixpkgs-unstable
$ sudo launchctl remove org.nixos.nix-daemon
$ sudo launchctl load /Library/LaunchDaemons/org.nixos.nix-daemon.plist
```
## Single-user all platforms
```console
$ nix-env --install --file '<nixpkgs>' --attr nix cacert -I nixpkgs=channel:nixpkgs-unstable
```

193
doc/manual/source/introduction.md Normal file
View file

@ -0,0 +1,193 @@
# Introduction
Nix is a _purely functional package manager_. This means that it
treats packages like values in purely functional programming languages
such as Haskell — they are built by functions that don’t have
side-effects, and they never change after they have been built. Nix
stores packages in the _Nix store_, usually the directory
`/nix/store`, where each package has its own unique subdirectory such
as
/nix/store/b6gvzjyb2pg0kjfwrjmg1vfhh54ad73z-firefox-33.1/
where `b6gvzjyb2pg0…` is a unique identifier for the package that
captures all its dependencies (it’s a cryptographic hash of the
package’s build dependency graph). This enables many powerful
features.
## Multiple versions
You can have multiple versions or variants of a package
installed at the same time. This is especially important when
different applications have dependencies on different versions of the
same package — it prevents the “DLL hell”. Because of the hashing
scheme, different versions of a package end up in different paths in
the Nix store, so they don’t interfere with each other.
An important consequence is that operations like upgrading or
uninstalling an application cannot break other applications, since
these operations never “destructively” update or delete files that are
used by other packages.
## Complete dependencies
Nix helps you make sure that package dependency specifications are
complete. In general, when you’re making a package for a package
management system like RPM, you have to specify for each package what
its dependencies are, but there are no guarantees that this
specification is complete. If you forget a dependency, then the
package will build and work correctly on _your_ machine if you have
the dependency installed, but not on the end user's machine if it's
not there.
Since Nix on the other hand doesn’t install packages in “global”
locations like `/usr/bin` but in package-specific directories, the
risk of incomplete dependencies is greatly reduced. This is because
tools such as compilers don’t search in per-packages directories such
as `/nix/store/5lbfaxb722zp…-openssl-0.9.8d/include`, so if a package
builds correctly on your system, this is because you specified the
dependency explicitly. This takes care of the build-time dependencies.
Once a package is built, runtime dependencies are found by scanning
binaries for the hash parts of Nix store paths (such as `r8vvq9kq…`).
This sounds risky, but it works extremely well.
## Multi-user support
Nix has multi-user support. This means that non-privileged users can
securely install software. Each user can have a different _profile_,
a set of packages in the Nix store that appear in the user’s `PATH`.
If a user installs a package that another user has already installed
previously, the package won’t be built or downloaded a second time.
At the same time, it is not possible for one user to inject a Trojan
horse into a package that might be used by another user.
## Atomic upgrades and rollbacks
Since package management operations never overwrite packages in the
Nix store but just add new versions in different paths, they are
_atomic_. So during a package upgrade, there is no time window in
which the package has some files from the old version and some files
from the new version — which would be bad because a program might well
crash if it’s started during that period.
And since packages aren’t overwritten, the old versions are still
there after an upgrade. This means that you can _roll back_ to the
old version:
```console
$ nix-env --upgrade --attr nixpkgs.some-package
$ nix-env --rollback
```
## Garbage collection
When you uninstall a package like this…
```console
$ nix-env --uninstall firefox
```
the package isn’t deleted from the system right away (after all, you
might want to do a rollback, or it might be in the profiles of other
users). Instead, unused packages can be deleted safely by running the
_garbage collector_:
```console
$ nix-collect-garbage
```
This deletes all packages that aren’t in use by any user profile or by
a currently running program.
## Functional package language
Packages are built from _Nix expressions_, which is a simple
functional language. A Nix expression describes everything that goes
into a package build task (a “derivation”): other packages, sources,
the build script, environment variables for the build script, etc.
Nix tries very hard to ensure that Nix expressions are
_deterministic_: building a Nix expression twice should yield the same
result.
Because it’s a functional language, it’s easy to support
building variants of a package: turn the Nix expression into a
function and call it any number of times with the appropriate
arguments. Due to the hashing scheme, variants don’t conflict with
each other in the Nix store.
## Transparent source/binary deployment
Nix expressions generally describe how to build a package from
source, so an installation action like
```console
$ nix-env --install --attr nixpkgs.firefox
```
_could_ cause quite a bit of build activity, as not only Firefox but
also all its dependencies (all the way up to the C library and the
compiler) would have to be built, at least if they are not already in the
Nix store. This is a _source deployment model_. For most users,
building from source is not very pleasant as it takes far too long.
However, Nix can automatically skip building from source and instead
use a _binary cache_, a web server that provides pre-built
binaries. For instance, when asked to build
`/nix/store/b6gvzjyb2pg0…-firefox-33.1` from source, Nix would first
check if the file `https://cache.nixos.org/b6gvzjyb2pg0….narinfo`
exists, and if so, fetch the pre-built binary referenced from there;
otherwise, it would fall back to building from source.
## Nix Packages collection
We provide a large set of Nix expressions containing hundreds of
existing Unix packages, the _Nix Packages collection_ (Nixpkgs).
## Managing build environments
Nix is extremely useful for developers as it makes it easy to
automatically set up the build environment for a package. Given a Nix
expression that describes the dependencies of your package, the
command `nix-shell` will build or download those dependencies if
they’re not already in your Nix store, and then start a Bash shell in
which all necessary environment variables (such as compiler search
paths) are set.
For example, the following command gets all dependencies of the
Pan newsreader, as described by [its
Nix expression](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/newsreaders/pan/default.nix):
```console
$ nix-shell '<nixpkgs>' --attr pan
```
You’re then dropped into a shell where you can edit, build and test
the package:
```console
[nix-shell]$ unpackPhase
[nix-shell]$ cd pan-*
[nix-shell]$ configurePhase
[nix-shell]$ buildPhase
[nix-shell]$ ./pan/gui/pan
```
## Portability
Nix runs on Linux and macOS.
## NixOS
NixOS is a Linux distribution based on Nix. It uses Nix not just for
package management but also to manage the system configuration (e.g.,
to build configuration files in `/etc`). This means, among other
things, that it is easy to roll back the entire configuration of the
system to an earlier state. Also, users can install software without
root privileges. For more information and downloads, see the [NixOS
homepage](https://nixos.org/).
## License
Nix is released under the terms of the [GNU LGPLv2.1 or (at your
option) any later
version](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html).

Some files were not shown because too many files have changed in this diff Show more