man: extend watchdog docs a bit

diff --git a/man/sd_notify.xml b/man/sd_notify.xml
index eb449555cb4437342c17d02cdcd8a5484783dc7f..a91c1bb4bf4c6893afaa7c85c6a34a0bbec3c7cf 100644 (file)
--- a/man/sd_notify.xml
+++ b/man/sd_notify.xml
@@ -156,12 +156,19 @@
                                 <term>WATCHDOG=1</term>
 
                                 <listitem><para>Tells systemd to
-                                update the watchdog timestamp.
-                                Services using this feature should do
-                                this in regular intervals. A watchdog
-                                framework can use the timestamps to
-                                detect failed
-                                services.</para></listitem>
+                                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_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>
                         </varlistentry>
                 </variablelist>
 

diff --git a/man/systemd.service.xml b/man/systemd.service.xml
index 233807d2b3313f6dc2a027051d96a964350a32b6..c57bce0ecf125446c834b409e4b0865f2ccc30d7 100644 (file)
--- a/man/systemd.service.xml
+++ b/man/systemd.service.xml
@@ -482,26 +482,29 @@
                                 is activated when the start-up is
                                 completed. The service must call
                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
-                                regularly with "WATCHDOG=1". If the
-                                time between two such calls is larger
-                                than the configured time then the
-                                service is placed in a failure
-                                state. By setting
-                                <varname>Restart=</varname>
-                                to <option>on-failure</option> or
+                                regularly with "WATCHDOG=1" (i.e. the
+                                "keep-alive ping"). If the time
+                                between two such calls is larger than
+                                the configured time then the service
+                                is placed in a failure state. By
+                                setting <varname>Restart=</varname> to
+                                <option>on-failure</option> or
                                 <option>always</option> the service
                                 will be automatically restarted. The
                                 time configured here will be passed to
                                 the executed service process in the
                                 <varname>WATCHDOG_USEC=</varname>
-                                environment variable. If
+                                environment variable. This allows
+                                daemons to automatically enable the
+                                keep-alive pinging logic if watchdog
+                                support is enabled for the service. If
                                 this option is used
                                 <varname>NotifyAccess=</varname> (see
                                 below) 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
+                                <varname>NotifyAccess=</varname> is
+                                not set, it will be implicitly set to
                                 <option>main</option>. Defaults to 0,
                                 which disables this
                                 feature.</para></listitem>