man: add note about sd_watchdog_enabled

diff --git a/man/systemd.service.xml b/man/systemd.service.xml
index c6ed75d158dcf52cbcddfbc3018b03a9e8f70ebb..20a71afe59a991300d193b281c8918b1654049da 100644 (file)
--- a/man/systemd.service.xml
+++ b/man/systemd.service.xml
@@ -517,7 +517,12 @@
         should be set to open access to the notification socket
         provided by systemd. If <varname>NotifyAccess=</varname> is
         not set, it will be implicitly set to <option>main</option>.
-        Defaults to 0, which disables this feature.</para></listitem>
+        Defaults to 0, which disables this feature. The service can
+        check whether the service manager expects watchdog keep-alive
+        notifications. See
+        <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+       for details.
+        </para></listitem>
       </varlistentry>
 
       <varlistentry>