* `nix-collect-garbage' now actually performs a garbage collection, it
doesn't just print the set of paths that should be deleted. So there is no more need to pipe the result into `nix-store --delete' (which doesn't even exist anymore).
This commit is contained in:
Eelco Dolstra
parent
818047881e
commit
fdec72c6cc
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@ -1,14 +1,16 @@
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<refentry>
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<refnamediv>
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<refname>nix-collect-garbage</refname>
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<refpurpose>determine the set of unreachable store paths</refpurpose>
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<refpurpose>remove unreachable store paths</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>nix-collect-garbage</command>
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<arg><option>--invert</option></arg>
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<arg><option>--no-successors</option></arg>
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<group choice='opt'>
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<arg choice='plain'><option>--print-live</option></arg>
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<arg choice='plain'><option>--print-dead</option></arg>
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</group>
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</cmdsynopsis>
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</refsynopsisdiv>
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@ -16,10 +18,22 @@
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<title>Description</title>
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<para>
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The command <command>nix-collect-garbage</command> determines
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the paths in the Nix store that are garbage, that is, not
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reachable from outside of the store. These paths can be safely
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deleted without affecting the integrity of the system.
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The command <command>nix-collect-garbage</command> performs a
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garbage collection on the Nix store: any paths in the Nix store
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that are garbage (not reachable from a set of root store
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expressions) are deleted.
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</para>
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<para>
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The roots of the garbage collector are the store expressions
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mentioned in the files in the directory
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<filename><replaceable>prefix</replaceable>/var/nix/gcroots</filename>.
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By default, the roots are all user environments in
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<filename><replaceable>prefix</replaceable>/var/nix/profiles</filename>.
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You can register other store expressions as roots by writing the
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full path of the store expression to an arbitrary file in the
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<filename>gcroots</filename> directory (or a subdirectory
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thereof).
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</para>
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</refsection>
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@ -30,27 +44,14 @@
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<variablelist>
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<varlistentry>
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<term><option>--invert</option></term>
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<term><option>--print-live</option> / <option>--print-dead</option></term>
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<listitem>
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<para>
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Causes the set of <emphasis>reachable</emphasis> paths to
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be printed, rather than the unreachable paths. These are
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the paths that may <emphasis>not</emphasis> be deleted.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--no-successors</option></term>
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<listitem>
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<para>
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Causes <command>nix-collect-garbage</command> not to
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follow successor relations. By default, if a derivation
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store expression is reachable, its successor (i.e., a
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closure store expression) is also considered to be
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reachable. This option is always safe, but garbage
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collecting successors may cause undesirable rebuilds later
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on.
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These options cause the set of live or dead paths to be
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printed, respectively, rather than performing an actual
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garbage collector. They correspond exactly with the
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sub-operations in <command>nix-store
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<option>--gc</option></command>.
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</para>
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</listitem>
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</varlistentry>
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@ -63,10 +64,10 @@
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<title>Examples</title>
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<para>
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To delete all unreachable paths, do the following:
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To delete all unreachable paths, just do:
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<screen>
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$ nix-collect-garbage | xargs nix-store --delete</screen>
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$ nix-collect-garbage</screen>
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</para>
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@ -135,17 +135,18 @@
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<!--######################################################################-->
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<refsection>
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<title>Operation <option>--delete</option></title>
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<title>Operation <option>--gc</option></title>
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<refsection>
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<title>Synopsis</title>
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<cmdsynopsis>
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<command>nix-store</command>
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<arg choice='plain'><option>--gc</option></arg>
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<group choice='req'>
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<arg choice='plain'><option>--print-live</option></arg>
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<arg choice='plain'><option>--print-dead</option></arg>
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<arg choice='plain'><option>--delete</option></arg>
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<arg choice='plain'><option>-d</option></arg>
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</group>
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<arg choice='plain' rep='repeat'><replaceable>paths</replaceable></arg>
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</cmdsynopsis>
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</refsection>
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@ -153,19 +154,64 @@
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<title>Description</title>
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<para>
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The operation <option>--delete</option> unconditionally deletes the
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paths <replaceable>paths</replaceable> from the Nix store. It is an
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error to attempt to delete paths outside of the store.
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The operation <option>--gc</option> performs a garbage
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collection on the Nix store. What it does specifically is
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determined by the sub-operation, which is one of the
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following:
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</para>
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<variablelist>
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<varlistentry>
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<term><option>--print-live</option></term>
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<listitem>
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<para>
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This operation prints on standard output the set of
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<quote>live</quote> store paths, which are all the store
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paths reachable from a set of <quote>root</quote> store
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expressions read from standard input. Live paths should
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never be deleted, since that would break consistency
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— it would become possible that applications are
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installed that reference things that are no longer
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present in the store.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--print-dead</option></term>
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<listitem>
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<para>
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This operation prints out on standard output the set of
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<quote>dead</quote> store paths, which is just the
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opposite of the set of live paths: any path in the store
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that is not live (with respect to the roots) is dead.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--delete</option></term>
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<listitem>
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<para>
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This operation performs an actual garbage collection.
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All dead paths are removed from the store.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>
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The set of root store expressions is read from standard input.
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Each line should contain exactly one store path.
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</para>
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<warning>
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<para>
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This operation should almost never be called directly, since no
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attempt is made to verify that no references exist to the paths to
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be deleted. Therefore, careless deletion can result in an
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inconsistent system. Deletion of paths in the store is done by the
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garbage collector (which uses <option>--delete</option> to delete
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unreferenced paths).
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You generally will want to use the command
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<command>nix-collect-garbage</command>, which figures out
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the roots and then calls this command automatically.
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</para>
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</warning>
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@ -131,7 +131,7 @@ $ nix-env -uBf nixpkgs-<replaceable>version</replaceable>/ '*'</screen>
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actual delete them:
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<screen>
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$ nix-collect-garbage | xargs nix-store --delete</screen>
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$ nix-collect-garbage</screen>
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</para>
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</listitem>
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@ -8,17 +8,17 @@ my $storeDir = "@storedir@";
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my %alive;
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my $gcOper = "--delete";
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my $keepSuccessors = 1;
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my $invert = 0;
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my @roots = ();
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# Parse the command line.
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foreach my $arg (@ARGV) {
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if ($arg eq "--no-successors") { $keepSuccessors = 0; }
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elsif ($arg eq "--invert") { $invert = 1; }
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else { die "unknown argument `$arg'" };
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if ($arg eq "--delete" || $arg eq "--print-live" || $arg eq "--print-dead") {
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$gcOper = $arg;
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} else { die "unknown argument `$arg'" };
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}
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@ -68,33 +68,15 @@ sub findRoots {
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findRoots 1, $rootsDir;
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# Determine all store paths reachable from the roots.
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my $extraarg = "";
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if ($keepSuccessors) { $extraarg = "--include-successors"; };
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my $pid = open2(\*READ, \*WRITE, "@bindir@/nix-store --query --requisites $extraarg @roots")
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or die "determining live paths";
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close WRITE;
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while (<READ>) {
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chomp;
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$alive{$_} = 1;
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if ($invert) { print "$_\n"; };
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# Run the collector with the roots we found.
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my $pid = open2(">&1", \*WRITE, "@bindir@/nix-store --gc $gcOper")
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or die "cannot run `nix-store --gc'";
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foreach my $root (@roots) {
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print WRITE "$root\n";
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}
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close READ;
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close WRITE;
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waitpid $pid, 0;
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$? == 0 or die "determining live paths";
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exit 0 if ($invert);
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# Using that information, find all store paths *not* reachable from
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# the roots.
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opendir(DIR, $storeDir) or die "cannot open directory $storeDir: $!";
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foreach my $name (readdir DIR) {
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next if ($name eq "." || $name eq "..");
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$name = "$storeDir/$name";
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if (!$alive{$name}) {
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print "$name\n";
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}
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}
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closedir DIR;
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$? == 0 or die "`nix-store --gc' failed";
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@ -222,7 +222,7 @@ static void opGC(Strings opFlags, Strings opArgs)
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if (flag == "--print-live") subOp = soPrintLive;
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else if (flag == "--print-dead") subOp = soPrintDead;
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else if (flag == "--delete") subOp = soDelete;
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else throw UsageError(format("bad sub-operation `%1% in GC") % flag);
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else throw UsageError(format("bad sub-operation `%1%' in GC") % flag);
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Paths roots;
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while (1) {
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