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* When we activate a descriptor in nix-switch, remember its hash.

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This allows us to find out all `live' packages on the system by
  doing

    nix closure $(cat /nix/var/nix/links/*.hash)

  which will print out the activated configurations and all packages
  referenced by them.  We could then garbage collect unused packages
  by deleting the difference between `nix listinst' and the set
  returned by `nix closure ...'.
This commit is contained in:
Eelco Dolstra 2003-04-09 12:46:44 +00:00
parent b762f4df7f
commit 30a6122f80
1 changed files with 7 additions and 1 deletions
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8
scripts/nix-switch
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@ -20,11 +20,17 @@ chomp $id;
my $nr = 0; my $nr = 0;
while (-e "$linkdir/$id-$nr") { $nr++; } while (-e "$linkdir/$id-$nr") { $nr++; }
my $link = "$linkdir/$id-$nr"; my $link = "$linkdir/$id-$nr";
print "$pkgdir\n";
# Create a symlink from $link to $pkgdir. # Create a symlink from $link to $pkgdir.
symlink($pkgdir, $link) or die "cannot create $link"; symlink($pkgdir, $link) or die "cannot create $link";
# Also store the hash of $pkgdir. This is useful for garbage
# collection and the like.
my $hashfile = "$linkdir/$id-$nr.hash";
open HASH, "> $hashfile" or die "cannot create $hashfile";
print HASH "$hash\n";
close HASH;
# Make $link the current generation by pointing $linkdir/current to # Make $link the current generation by pointing $linkdir/current to
# it. The rename() system call is supposed to be essentially atomic # it. The rename() system call is supposed to be essentially atomic
# on Unix. That is, if we have links `current -> X' and `new_current # on Unix. That is, if we have links `current -> X' and `new_current