nix-super/doc/manual/nix-collect-garbage.xml

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<refmeta>
  <refentrytitle>nix-collect-garbage</refentrytitle>
  <manvolnum>1</manvolnum>
  <refmiscinfo class="source">Nix</refmiscinfo>
  <refmiscinfo class="version"><xi:include href="version.txt" parse="text"/></refmiscinfo>
</refmeta>

<refnamediv>
  <refname>nix-collect-garbage</refname>
  <refpurpose>delete unreachable store paths</refpurpose>
</refnamediv>

<refsynopsisdiv>
  <cmdsynopsis>
    <command>nix-collect-garbage</command>
    <arg><option>--delete-old</option></arg>
    <arg><option>-d</option></arg>
    <group choice='opt'>
      <arg choice='plain'><option>--print-roots</option></arg>
      <arg choice='plain'><option>--print-live</option></arg>
      <arg choice='plain'><option>--print-dead</option></arg>
      <arg choice='plain'><option>--delete</option></arg>
    </group>
  </cmdsynopsis>
</refsynopsisdiv>

<refsection><title>Description</title>

<para>The command <command>nix-collect-garbage</command> is mostly an
alias of <link linkend="rsec-nix-store-gc"><command>nix-store
--gc</command></link>, that is, it deletes all unreachable paths in
the Nix store to clean up your system.  However, it provides an
additional option <option>-d</option> (<option>--delete-old</option>)
that deletes all old generations of all profiles in
<filename>/nix/var/nix/profiles</filename> by invoking
<literal>nix-env --delete-generations old</literal> on all profiles.
Of course, this makes rollbacks to previous configurations
impossible.</para>

</refsection>

<refsection><title>Example</title>

<para>To delete from the Nix store everything that is not used by the
current generations of each profile, do

<screen>
$ nix-collect-garbage -d</screen>

</para>

</refsection>

</refentry>