Merge pull request #17497 from anitazha/randomizeonce

timer: add new feature FixedRandomDelay=

man/systemd.timer.xml

@@ -268,6 +268,18 @@
         <varname>AccuracySec=1us</varname>.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>FixedRandomDelay=</varname></term>
+
+        <listitem><para>Takes a boolean argument. If true, some amount of time between 0 and
+        <varname>RandomizedDelaySec=</varname> is chosen and added as the delay for each timer iteration. As this
+        delay will not be recalculated on each run, this effectively creates a fixed offset for each iteration.
+        The distribution between 0 and <varname>RandomizedDelaySec=</varname> is deterministic and based on
+        a combination of the machine ID, whether the timer is run by the user/system manager, the service manager's
+        user ID, and the timer's unit name. Has no effect if
+        <varname>RandomizedDelaySec=</varname> is set to 0. Defaults to <option>false</option>.</para></listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><varname>OnClockChange=</varname></term>
         <term><varname>OnTimezoneChange=</varname></term>
@@ -276,7 +288,7 @@
         when the system clock (<constant>CLOCK_REALTIME</constant>) jumps relative to the monotonic clock
         (<constant>CLOCK_MONOTONIC</constant>), or when the local system timezone is modified. These options
         can be used alone or in combination with other timer expressions (see above) within the same timer
-        unit. These options default to false.</para></listitem>
+        unit. These options default to <option>false</option>.</para></listitem>
       </varlistentry>
 
       <varlistentry>
@@ -301,7 +313,7 @@
         is nonetheless subject to the delay imposed by <varname>RandomizedDelaySec=</varname>.
         This is useful to catch up on missed runs of the service when the system was powered down. Note that
         this setting only has an effect on timers configured with <varname>OnCalendar=</varname>. Defaults to
-        <varname>false</varname>.</para>
+        <option>false</option>.</para>
 
         <para>Use <command>systemctl clean --what=state …</command> on the timer unit to remove the timestamp
         file maintained by this option from disk. In particular, use this command before uninstalling a timer
@@ -317,7 +329,7 @@
         from suspend, should it be suspended and if the system supports this. Note that this option will only
         make sure the system resumes on the appropriate times, it will not take care of suspending it again
         after any work that is to be done is finished. Defaults to
-        <varname>false</varname>.</para>
+        <option>false</option>.</para>
 
         <para>Note that this functionality requires privileges and is thus generally only available in the
         system service manager.</para>
@@ -343,7 +355,7 @@
         <varname>RemainAfterElapse=</varname> is on, starting the timer a second time has no effect. However,
         if <varname>RemainAfterElapse=</varname> is off and the timer unit was already unloaded, it can be
         started again, and thus the service can be triggered multiple times. Defaults to
-        <varname>yes</varname>.</para></listitem>
+        <option>true</option>.</para></listitem>
       </varlistentry>
     </variablelist>
   </refsect1>