journald: add support for wall forwarding

[elogind.git] / man / systemd.timer.xml

diff --git a/man/systemd.timer.xml b/man/systemd.timer.xml
index fa67d59a22acac7eec7982019bb5ee5ce6c79440..98d4f7b7b9cef66dd82060295fea66f214905f8a 100644 (file)
--- a/man/systemd.timer.xml
+++ b/man/systemd.timer.xml
@@ -128,7 +128,7 @@
                                 combined of the same and of different
                                 types. For example, by combining
                                 <varname>OnBootSec=</varname> and
                                 combined of the same and of different
                                 types. For example, by combining
                                 <varname>OnBootSec=</varname> and

-                                <varname>OnUnitActiveSec=</varname> it is
+                                <varname>OnUnitActiveSec=</varname>, it is

                                 possible to define a timer that
                                 elapses in regular intervals and
                                 activates a specific service each
                                 possible to define a timer that
                                 elapses in regular intervals and
                                 activates a specific service each


@@ -141,7 +141,7 @@
                                 also include time units. Example:
                                 "OnBootSec=5h 30min" means 5 hours and
                                 30 minutes after boot-up. For details
                                 also include time units. Example:
                                 "OnBootSec=5h 30min" means 5 hours and
                                 30 minutes after boot-up. For details

-                                about the syntax of time spans see
+                                about the syntax of time spans, see

                                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 
                                 <para>If a timer configured with
                                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 
                                 <para>If a timer configured with


@@ -163,7 +163,14 @@
                                 to any of these options, the list of
                                 timers is reset, and all prior
                                 assignments will have no
                                 to any of these options, the list of
                                 timers is reset, and all prior
                                 assignments will have no

-                                effect.</para></listitem>
+                                effect.</para>
+
+                                <para>Note that timers do not
+                                necessarily expire at the precise
+                                time configured with these settings,
+                                as they are subject to the
+                                <varname>AccuracySec=</varname>
+                                setting below.</para></listitem>

 
                         </varlistentry>
 
 
                         </varlistentry>
 


@@ -171,16 +178,61 @@
                                 <term><varname>OnCalendar=</varname></term>
 
                                 <listitem><para>Defines realtime
                                 <term><varname>OnCalendar=</varname></term>
 
                                 <listitem><para>Defines realtime

-                                (i.e. wallclock) timers via calendar
+                                (i.e. wallclock) timers with calendar

                                 event expressions. See
                                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                                 for more information on the syntax of
                                 event expressions. See
                                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                                 for more information on the syntax of

-                                calendar event expressions. Otherwise
+                                calendar event expressions. Otherwise,

                                 the semantics are similar to
                                 <varname>OnActiveSec=</varname> and
                                 the semantics are similar to
                                 <varname>OnActiveSec=</varname> and

-                                related settings.</para></listitem>
+                                related settings.</para>
+
+                                <para>Note that timers do not
+                                necessarily expire at the precise
+                                time configured with this setting,
+                                as it is subject to the
+                                <varname>AccuracySec=</varname>
+                                setting below.</para></listitem>

                         </varlistentry>
 
                         </varlistentry>
 

+                        <varlistentry>
+                                <term><varname>AccuracySec=</varname></term>
+
+                                <listitem><para>Specify the accuracy
+                                the timer shall elapse with. Defaults
+                                to 1min. The timer is scheduled to
+                                elapse within a time window starting
+                                with the time specified in
+                                <varname>OnCalendar=</varname>,
+                                <varname>OnActiveSec=</varname>,
+                                <varname>OnBootSec=</varname>,
+                                <varname>OnStartupSec=</varname>,
+                                <varname>OnUnitActiveSec=</varname> or
+                                <varname>OnUnitInactiveSec=</varname>
+                                and ending the time configured with
+                                <varname>AccuracySec=</varname>
+                                later. Within this time window, the
+                                expiry time will be placed at a
+                                host-specific, randomized but stable
+                                position that is synchronized between
+                                all local timer units. This is done in
+                                order to distribute the wake-up time
+                                in networked installations, as well as
+                                optimizing power consumption to
+                                suppress unnecessary CPU wake-ups. To
+                                get best accuracy, set this option to
+                                1us. Note that the timer is still
+                                subject to the timer slack configured
+                                via
+                                <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>'s
+                                <varname>TimerSlackNSec=</varname>
+                                setting. See
+                                <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+                                for details. To optimize power
+                                consumption, make sure to set this
+                                value as high as possible and as low
+                                as necessary.</para></listitem>
+                        </varlistentry>

                         <varlistentry>
                                 <term><varname>Unit=</varname></term>
 
                         <varlistentry>
                                 <term><varname>Unit=</varname></term>
 


@@ -208,7 +260,9 @@
                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                           <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,

-                          <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                          <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>

                   </para>
         </refsect1>
 
                   </para>
         </refsect1>