+
+ <varlistentry>
+ <term>WATCHDOG=1</term>
+
+ <listitem><para>Tells systemd to
+ update the watchdog timestamp. This is
+ the keep-alive ping that services need
+ to issue in regular intervals if
+ <varname>WatchdogSec=</varname> is
+ enabled for it. See
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details. It is recommended to send
+ this message if the
+ <varname>$WATCHDOG_PID</varname>
+ environment variable has been set to
+ the PID of the service process, in
+ every half the time interval that is
+ specified in the
+ <varname>$WATCHDOG_USEC</varname>
+ environment variable. See
+ <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for details.</para></listitem>
+ </varlistentry>