man: document that machinectl set-limit creates a btrfs loopback too

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Lennart Poettering 2015-03-02 19:35:50 +01:00
parent 4cee5eede2
commit 7de304525d

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@ -508,16 +508,32 @@
<term><command>set-limit</command> [<replaceable>NAME</replaceable>] <replaceable>BYTES</replaceable></term>
<listitem><para>Sets the maximum size in bytes a specific
container or VM image, or all images may grow up to
(quota). Takes either one or two parameters. The first,
container or VM image, or all images may grow up to on disk
(disk quota). Takes either one or two parameters. The first,
optional parameter refers to a container or VM image name. If
specified the size limit of the specified images is
changed. If omitted the overall size limit of the sum of all
images stored locally is changed. The final argument specifies
the size limit in bytes, possibly suffixed by the usual K, M,
G, T units. If the size limit shall be disabled, specify
<literal>-</literal> as size. This operation is currently only
supported on btrfs subvolume images.</para></listitem>
specified the size limit of the specified image is changed. If
omitted the overall size limit of the sum of all images stored
locally is changed. The final argument specifies the size
limit in bytes, possibly suffixed by the usual K, M, G, T
units. If the size limit shall be disabled, specify
<literal>-</literal> as size.</para>
<para>Note that per-container size limits are only supported
on btrfs file systems. Also note that if
<command>set-limit</command> is invoked without image
parameter, and <filename>/var/lib/machines</filename> is
empty, and the directory is not located on btrfs, a btrfs
loopback file is implicitly created as
<filename>/var/lib/machines.raw</filename> with the given
size, and mounted to
<filename>/var/lib/machines</filename>. The size of the
loopback may later be readjusted with
<command>set-limit</command>, as well. If such a
loopback-mounted <filename>/var/lib/machines</filename>
directory is used <command>set-limit</command> without image
name alters both the quota setting within the file system as
well as the loopback file and file system size
itself.</para></listitem>
</varlistentry>
</variablelist></refsect2>
@ -686,6 +702,17 @@
<filename>/var/lib/machines/</filename> to make them available for
control with <command>machinectl</command>.</para>
<para>Note that many image operations are only supported,
efficient or atomic on btrfs file systems. Due to this, if the
<command>pull-tar</command>, <command>pull-raw</command>,
<command>pull-dkr</command> and <command>set-limit</command>
commands notice that <filename>/var/lib/machines</filename> is
empty and not located on btrfs, they will implicitly set up a
loopback file <filename>/var/lib/machines.raw</filename>
containing a btrfs file system that is mounted to
<filename>/var/lib/machines</filename>. The size of this loopback
file may be controlled dynamically with <command>set-limit</command>.</para>
<para>Disk images are understood by
<citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
and <command>machinectl</command> in three formats:</para>