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LocalStore: Allow the physical and logical store directories to differ

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This is primarily to subsume the functionality of the
copy-from-other-stores substituter. For example, in the NixOS
installer, we can now do (assuming we're in the target chroot, and the
Nix store of the installation CD is bind-mounted on /tmp/nix):

  $ nix-build ... --option substituters 'local?state=/tmp/nix/var&real=/tmp/nix/store'

However, unlike copy-from-other-stores, this also allows write access
to such a store. One application might be fetching substitutes for
/nix/store in a situation where the user doesn't have sufficient
privileges to create /nix, e.g.:

  $ NIX_REMOTE="local?state=/home/alice/nix/var&real=/home/alice/nix/store" nix-build ...
This commit is contained in:
Eelco Dolstra 2016-06-02 15:08:18 +02:00
parent 064816ab98
commit 4494000e04
7 changed files with 68 additions and 158 deletions
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103
scripts/copy-from-other-stores.pl.in
View file

@ -1,103 +0,0 @@
#! @perl@ -w @perlFlags@
use utf8;
use strict;
use File::Basename;
use IO::Handle;
my $binDir = $ENV{"NIX_BIN_DIR"} || "@bindir@";
STDOUT->autoflush(1);
binmode STDERR, ":encoding(utf8)";
my @remoteStoresAll = split ':', ($ENV{"NIX_OTHER_STORES"} or "");
my @remoteStores;
foreach my $dir (@remoteStoresAll) {
push @remoteStores, glob($dir);
}
exit if scalar @remoteStores == 0;
print "\n";
$ENV{"NIX_REMOTE"} = "";
sub findStorePath {
my $storePath = shift;
foreach my $store (@remoteStores) {
my $sourcePath = "$store/store/" . basename $storePath;
next unless -e $sourcePath || -l $sourcePath;
$ENV{"NIX_DB_DIR"} = "$store/var/nix/db";
return ($store, $sourcePath) if
system("$binDir/nix-store --check-validity $storePath") == 0;
}
return undef;
}
if ($ARGV[0] eq "--query") {
while (<STDIN>) {
chomp;
my ($cmd, @args) = split " ", $_;
if ($cmd eq "have") {
foreach my $storePath (@args) {
print "$storePath\n" if defined findStorePath($storePath);
}
print "\n";
}
elsif ($cmd eq "info") {
foreach my $storePath (@args) {
my ($store, $sourcePath) = findStorePath($storePath);
next unless defined $store;
$ENV{"NIX_DB_DIR"} = "$store/var/nix/db";
my $deriver = `$binDir/nix-store --query --deriver $storePath`;
die "cannot query deriver of ‘$storePath’" if $? != 0;
chomp $deriver;
$deriver = "" if $deriver eq "unknown-deriver";
my @references = split "\n",
`$binDir/nix-store --query --references $storePath`;
die "cannot query references of ‘$storePath’" if $? != 0;
my $narSize = `$binDir/nix-store --query --size $storePath`;
die "cannot query size of ‘$storePath’" if $? != 0;
chomp $narSize;
print "$storePath\n";
print "$deriver\n";
print scalar @references, "\n";
print "$_\n" foreach @references;
print "0\n";
print "$narSize\n";
}
print "\n";
}
else { die "unknown command ‘$cmd’"; }
}
}
elsif ($ARGV[0] eq "--substitute") {
die unless scalar @ARGV == 3;
my $storePath = $ARGV[1];
my $destPath = $ARGV[2];
my ($store, $sourcePath) = findStorePath $storePath;
die unless $store;
print STDERR "\n*** Copying ‘$storePath’ from ‘$sourcePath’\n\n";
system("@coreutils@/cp", "-rpd", $sourcePath, $destPath) == 0
or die "cannot copy ‘$sourcePath’ to ‘$storePath’";
print "\n"; # no hash to verify
}
else { die; }