man: document nspawn's new --volatile switch

diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index 950558feec085c53193ab3c2f933a09fa9af51c9..cb0605bcd10d67e6cfeef909d8058d27d137a883 100644 (file)
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -644,6 +644,49 @@
                                 of the container OS itself.</para></listitem>
                         </varlistentry>
 
+                        <varlistentry>
+                                <term><option>--volatile</option><replaceable>=MODE</replaceable></term>
+
+                                <listitem><para>Boots the container in
+                                volatile (ephemeral) mode. When no
+                                mode parameter is passed or when mode
+                                is specified as <literal>yes</literal>
+                                full volatile mode is enabled. This
+                                means the root directory is mounted as
+                                mostly unpopulated
+                                <literal>tmpfs</literal> instance, and
+                                <filename>/usr</filename> from the OS
+                                tree is mounted into it, read-only
+                                (the system thus starts up with
+                                read-only OS resources, but pristine
+                                state and configuration, any changes
+                                to the either are lost on
+                                shutdown). When the mode parameter is
+                                specified as <literal>state</literal>
+                                the OS tree is mounted read-only, but
+                                <filename>/var</filename> is mounted
+                                as <literal>tmpfs</literal> instance
+                                into it (the system thus starts up
+                                with read-only OS resources and
+                                configuration, but prestine state, any
+                                changes to the latter are lost on
+                                shutdown). When the mode parameter is
+                                specified as <literal>no</literal>
+                                (the default) the whole OS tree is made
+                                available writable.</para>
+
+                                <para>Note that setting this to
+                                <literal>yes</literal> or
+                                <literal>state</literal> will only
+                                work correctly with operating systems
+                                in the container that can boot up with
+                                only <filename>/usr</filename>
+                                mounted, and are able to populate
+                                <filename>/var</filename>
+                                automatically, as
+                                needed.</para></listitem>
+                        </varlistentry>
+
                         <xi:include href="standard-options.xml" xpointer="help" />
                         <xi:include href="standard-options.xml" xpointer="version" />
                 </variablelist>