<literal>persistent</literal>, data will be stored preferably on disk, i.e. below the
<filename>/var/log/journal</filename> hierarchy (which is created if needed), with a fallback to
<filename>/run/log/journal</filename> (which is created if needed), during early boot and if the disk
- is not writable. <literal>auto</literal> is similar to <literal>persistent</literal> but the
- directory <filename>/var/log/journal</filename> is not created if needed, so that its existence
- controls where log data goes. <literal>none</literal> turns off all storage, all log data received
- will be dropped. Forwarding to other targets, such as the console, the kernel log buffer, or a syslog
- socket will still work however. Defaults to <literal>auto</literal> in the default journal namespace,
- and <literal>persistent</literal> in all others.</para></listitem>
+ is not writable. <literal>auto</literal> behaves like <literal>persistent</literal> if the
+ <filename>/var/log/journal</filename> directory exists, and <literal>volatile</literal> otherwise
+ (the existence of the directory controls the storage mode). <literal>none</literal> turns off all
+ storage, all log data received will be dropped (but forwarding to other targets, such as the console,
+ the kernel log buffer, or a syslog socket will still work). Defaults to <literal>auto</literal> in
+ the default journal namespace, and <literal>persistent</literal> in all others.</para>
+
+ <para>Note that when this option is changed to <literal>volatile</literal>, existing persistent data
+ is not removed. In the other direction,
+ <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> with
+ the <option>--flush</option> option may be used to move volatile data to persistent storage.</para>
+ </listitem>
</varlistentry>
<varlistentry>