- for details. It is recommended to send
- this message if the
- <varname>WATCHDOG_USEC=</varname>
- environment variable has been set for
- the service process, in every half the
- time interval that is specified in the
- variable.</para></listitem>
+ for information how to enable this
+ functionality and
+ <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for the details of how the service can
+ check if the the watchdog is enabled.
+ </para></listitem>
+ </varlistentry>
+
+
+ <varlistentry>
+ <term>FDSTORE=1</term>
+
+ <listitem><para>Stores additional file
+ descriptors in the service
+ manager. File descriptors sent this
+ way will be maintained per-service by
+ the service manager and be passed
+ again using the usual file descriptor
+ passing logic on the next invocation
+ of the service (see
+ <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>). This
+ is useful for implementing service
+ restart schemes where services
+ serialize their state to
+ <filename>/run</filename>, push their
+ file descriptors to the system
+ manager, and are then restarted,
+ retrieving their state again via
+ socket passing and
+ <filename>/run</filename>. Note that
+ the service manager will accept
+ messages for a service only if
+ <varname>FileDescriptorStoreMax=</varname>
+ is set to non-zero for it (defaults to
+ zero). See
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details. Multiple arrays of file
+ descriptors may be sent in seperate
+ messages, in which case the arrays are
+ combined. Note that the service
+ manager removes duplicate file
+ descriptors before passing them to the
+ service. Use
+ <function>sd_pid_notify_with_fds()</function>
+ to send messages with
+ <literal>FDSTORE=1</literal>, see
+ below.</para></listitem>