- 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>