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lix/doc/manual/nix-collect-garbage.xml
Eelco Dolstra eb233e728f * `--min-age' flag in nix-store and nix-collect-garbage to only delete
unreachable paths that haven't been used for N hours.  For instance,
  `nix-collect-garbage --min-age 168' only deletes paths that haven't
  been accessed in the last week.

  This is useful for instance in the build farm where many derivations
  can be shared between consecutive builds, and we wouldn't want a
  garbage collect to throw them all away.  We could of course register
  them as roots, but then we'd to unregister them at some point, which
  would be a pain to manage.  The `--min-age' flag gives us a sort of
  MRU caching scheme.

  BUG: this really shouldn't be in gc.cc since that violates
  mechanism/policy separation.
2004-08-25 16:54:08 +00:00

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<refentry>
<refnamediv>
<refname>nix-collect-garbage</refname>
<refpurpose>remove unreachable store paths</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>nix-collect-garbage</command>
<group choice='opt'>
<arg choice='plain'><option>--print-live</option></arg>
<arg choice='plain'><option>--print-dead</option></arg>
</group>
<arg><option>--min-age</option> <replaceable>age</replaceable></arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsection>
<title>Description</title>
<para>
The command <command>nix-collect-garbage</command> performs a
garbage collection on the Nix store: any paths in the Nix store
that are garbage (not reachable from a set of root store
expressions) are deleted.
</para>
<para>
The roots of the garbage collector are the store expressions
mentioned in the files in the directory
<filename><replaceable>prefix</replaceable>/var/nix/gcroots</filename>.
By default, the roots are all user environments in
<filename><replaceable>prefix</replaceable>/var/nix/profiles</filename>.
You can register other store expressions as roots by writing the
full path of the store expression to an arbitrary file in the
<filename>gcroots</filename> directory (or a subdirectory
thereof).
</para>
</refsection>
<refsection>
<title>Options</title>
<variablelist>
<varlistentry>
<term><option>--print-live</option> / <option>--print-dead</option></term>
<listitem>
<para>
These options cause the set of live or dead paths to be
printed, respectively, rather than performing an actual
garbage collector. They correspond exactly with the
sub-operations in <command>nix-store
<option>--gc</option></command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--min-age</option> <replaceable>age</replaceable></term>
<listitem>
<para>
This option corresponds to the <option>--min-age</option>
option in <command>nix-store <option>--gc</option></command>.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Examples</title>
<para>
To delete all unreachable paths, just do:
<screen>
$ nix-collect-garbage</screen>
</para>
</refsection>
</refentry>