man: document LogNamespace= unit setting

diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index b7f44c9473d0cd3470ef9b89a9166503188ec0f3..8f1695ad293f6113a4b32f58c18822687c4f8928 100644 (file)
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -70,6 +70,10 @@
       <option>syslog</option> or <option>kmsg</option> (or their combinations with console output, see below)
       automatically acquire dependencies of type <varname>After=</varname> on
       <filename>systemd-journald.socket</filename>.</para></listitem>
+
+      <listitem><para>Units using <varname>LogNamespace=</varname> will automatically gain ordering and
+      requirement dependencies on the two socket units associated with
+      <filename>systemd-journald@.service</filename> instances.</para></listitem>
     </itemizedlist>
   </refsect1>
 
@@ -2254,6 +2258,36 @@ StandardInputData=SWNrIHNpdHplIGRhIHVuJyBlc3NlIEtsb3BzLAp1ZmYgZWVtYWwga2xvcHAncy
         </para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>LogNamespace=</varname></term>
+
+        <listitem><para>Run the unit's processes in the specified journal namespace. Expects a short
+        user-defined string identifying the namespace. If not used the processes of the service are run in
+        the default journal namespace, i.e. their log stream is collected and processed by
+        <filename>systemd-journald.service</filename>. If this option is used any log data generated by
+        processes of this unit (regardless if via the <function>syslog()</function>, journal native logging
+        or stdout/stderr logging) is collected and processed by an instance of the
+        <filename>systemd-journald@.service</filename> template unit, which manages the specified
+        namespace. The log data is stored in a data store independent from the default log namespace's data
+        store. See
+        <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+        for details about journal namespaces.</para>
+
+        <para>Internally, journal namespaces are implemented through Linux mount namespacing and
+        over-mounting the directory that contains the relevant <constant>AF_UNIX</constant> sockets used for
+        logging in the unit's mount namespace. Since mount namespaces are used this setting disconnects
+        propagation of mounts from the unit's processes to the host, similar to how
+        <varname>ReadOnlyPaths=</varname> and similar settings (see above) work. Journal namespaces may hence
+        not be used for services that need to establish mount points on the host.</para>
+
+        <para>When this option is used the unit will automatically gain ordering and requirement dependencies
+        on the two socket units associated with the <filename>systemd-journald@.service</filename> instance
+        so that they are automatically established prior to the unit starting up. Note that when this option
+        is used log output of this service does not appear in the regular
+        <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+        output, unless the <option>--namespace=</option> option is used.</para></listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><varname>SyslogIdentifier=</varname></term>