mirror of https://github.com/NixOS/nix synced 2025-06-25 06:31:14 +02:00

John Ericson cafefed421 Rename to "content-address*ing* derivation"

"content-address*ed*" derivation is misleading because all derivations
are *themselves* content-addressed. What may or may not be
content-addressed is not derivation itself, but the *output* of the
derivation.

The outputs are not *part* of the derivation (for then the derivation
wouldn't be complete before we built it) but rather separate entities
produced by the derivation.

"content-adddress*ed*" is not correctly because it can only describe
what the derivation *is*, and that is not what we are trying to do.

"content-address*ing*" is correct because it describes what the
derivation *does* --- it produces content-addressed data.

2025-02-10 01:12:56 -05:00

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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-addressing 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 executable
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.

The resulting paths are printed on standard output. For non-derivation arguments, the argument itself is printed.

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.

Examples

This operation is typically used to build store derivations produced by nix-instantiate:

$ nix-store --realise $(nix-instantiate ./test.nix)
/nix/store/31axcgrlbfsxzmfff1gyj1bf62hvkby2-aterm-2.3.1

This is essentially what nix-build does.

To test whether a previously-built derivation is deterministic:

$ nix-build '<nixpkgs>' --attr hello --check -K

Use nix-store --read-log to show the stderr and stdout of a build:

$ nix-store --read-log $(nix-instantiate ./test.nix)

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