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* Some GC documentation.

This commit is contained in:
Eelco Dolstra 2005-04-05 11:30:56 +00:00
parent 6c8cf567b8
commit 229252941a
2 changed files with 52 additions and 42 deletions
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10
doc/manual/nix-collect-garbage.xml
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@ -57,16 +57,6 @@
</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>

84
doc/manual/nix-store.xml
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@ -167,24 +167,37 @@ output.</para>
<title>Description</title>
<para>
The operation <option>--gc</option> performs a garbage
collection on the Nix store. What it does specifically is
determined by the sub-operation, which is one of the
following:
Without additional flags, the operation <option>--gc</option>
performs a garbage collection on the Nix store. That is, all
paths in the Nix store not reachable via file system
references from a set of <quote>roots</quote>, are deleted.
</para>
<para>
The following flags may be specified:
</para>
<variablelist>
<varlistentry>
<term><option>--print-roots</option></term>
<listitem>
<para>
This operation prints on standard output the set of
roots used by the garbage collector.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--print-live</option></term>
<listitem>
<para>
This operation prints on standard output the set of
<quote>live</quote> store paths, which are all the store
paths reachable from a set of <quote>root</quote> store
expressions read from standard input. Live paths should
never be deleted, since that would break consistency —
it would become possible that applications are installed
paths reachable from the roots. Live paths should never
be deleted, since that would break consistency — it
would become possible that applications are installed
that reference things that are no longer present in the
store.
</para>
@ -215,32 +228,39 @@ output.</para>
</variablelist>
<para>
The set of root store expressions is read from standard input.
Each line should contain exactly one store path.
</para>
<para>
The option <option>--min-age</option> specifies a minimum time
in hours that an unreachable store path must not have been
used before it is considered dead. The default is 0 (consider
all unreachable store paths dead). Whether a store path has
been used is determined by looking at its access time
(<literal>atime</literal>), so this does not work if the store
is located on a file system that has the
<literal>noatime</literal> option set.
</para>
<warning>
<para>
You generally will want to use the command
<command>nix-collect-garbage</command>, which figures out
the roots and then calls this command automatically.
</para>
</warning>
</refsection>
<refsection>
<title>Roots</title>
<para>The roots of the garbage collector are all store paths to
which there are symlinks in the
directory <filename><replaceable>prefix</replaceable>/nix/var/nix/gcroots</filename>.
For instance, the following command makes the
path <filename>/nix/store/d718ef...-foo</filename> a root of
the collector:
<screen>
$ ln -s /nix/store/d718ef...-foo /nix/var/nix/gcroots/bar</screen>
That is, after this command, the garbage collector will not
remove <filename>/nix/store/d718ef...-foo</filename> or any of
its dependencies.</para>
<para>Subdirectories
of <filename><replaceable>prefix</replaceable>/nix/var/nix/gcroots</filename>
are also searched for symlinks. Symlinks to non-store paths are
followed and searched for roots, but TODO.</para>
</refsection>
<refsection>
<title>Configuration file</title>
<para>TODO</para>
</refsection>
</refsection>