Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2 of the License, or
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- General Public License for more details.
+ Lesser General Public License for more details.
- You should have received a copy of the GNU General Public License
+ You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refnamediv>
<refname>systemd.timer</refname>
- <refpurpose>systemd timer configuration files</refpurpose>
+ <refpurpose>Timer unit configuration</refpurpose>
</refnamediv>
<refsynopsisdiv>
- <para><filename>systemd.timer</filename></para>
+ <para><filename><replaceable>timer</replaceable>.timer</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>A unit configuration file whose name ends in
- <filename>.timer</filename> encodes information about
+ <literal>.timer</literal> encodes information about
a timer controlled and supervised by systemd, for
timer-based activation.</para>
matching service <filename>foo.service</filename>. The
unit to activate may be controlled by
<varname>Unit=</varname> (see below).</para>
+
+ <para>Unless <varname>DefaultDependencies=</varname>
+ is set to <option>false</option>, timer units will
+ implicitly have dependencies of type
+ <varname>Conflicts=</varname> and
+ <varname>Before=</varname> on
+ <filename>shutdown.target</filename>. These ensure
+ that timer units are stopped cleanly prior to system
+ shutdown. Only timer units involved with early boot or
+ late system shutdown should disable this
+ option.</para>
</refsect1>
<refsect1>
defines. The options specific to the [Timer] section
of timer units are the following:</para>
- <variablelist>
+ <variablelist class='unit-directives'>
<varlistentry>
- <term><varname>OnActive=</varname></term>
- <term><varname>OnBootup=</varname></term>
- <term><varname>OnStartup=</varname></term>
- <term><varname>OnUnitActive=</varname></term>
- <term><varname>OnUnitInactive=</varname></term>
+ <term><varname>OnActiveSec=</varname></term>
+ <term><varname>OnBootSec=</varname></term>
+ <term><varname>OnStartupSec=</varname></term>
+ <term><varname>OnUnitActiveSec=</varname></term>
+ <term><varname>OnUnitInactiveSec=</varname></term>
- <listitem><para>Defines timers
+ <listitem><para>Defines monotonic timers
relative to different starting points:
- <varname>OnActive=</varname> defines a
+ <varname>OnActiveSec=</varname> defines a
timer relative to the moment the timer
itself is
- activated. <varname>OnBootup=</varname>
+ activated. <varname>OnBootSec=</varname>
defines a timer relative to when the
machine was booted
- up. <varname>OnStartup=</varname>
+ up. <varname>OnStartupSec=</varname>
defines a timer relative to when
- systemd was
- started. <varname>OnUnitActive=</varname>
+ systemd was first
+ started. <varname>OnUnitActiveSec=</varname>
defines a timer relative to when the
unit the timer is activating was last
- activated. <varname>OnUnitInactive=</varname>
+ activated. <varname>OnUnitInactiveSec=</varname>
defines a timer relative to when the
unit the timer is activating was last
deactivated.</para>
<para>Multiple directives may be
combined of the same and of different
types. For example, by combining
- <varname>OnBoot=</varname> and
- <varname>OnUnitActive=</varname> it is
+ <varname>OnBootSec=</varname> and
+ <varname>OnUnitActiveSec=</varname>, it is
possible to define a timer that
elapses in regular intervals and
activates a specific service each
<para>The arguments to the directives
are time spans configured in
- seconds. Example: "OnBoot=50" means
+ seconds. Example: "OnBootSec=50" means
50s after boot-up. The argument may
also include time units. Example:
- "OnBoot=5h 30min" means 5 hours and 30
- minutes after boot-up. For details
- about the syntax of time spans see
+ "OnBootSec=5h 30min" means 5 hours and
+ 30 minutes after boot-up. For details
+ about the syntax of time spans, see
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
<para>If a timer configured with
- <varname>OnBootup=</varname> or
- <varname>OnStartup=</varname> is
+ <varname>OnBootSec=</varname> or
+ <varname>OnStartupSec=</varname> is
already in the past when the timer
unit is activated, it will immediately
elapse and the configured unit is
started. This is not the case for
timers defined in the other
- directives.</para></listitem>
+ directives.</para>
<para>These are monotonic timers,
independent of wall-clock time and timezones. If the
computer is temporarily suspended, the
monotonic clock stops too.</para>
+ <para>If the empty string is assigned
+ to any of these options, the list of
+ timers is reset, and all prior
+ assignments will have no
+ 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>
+ <term><varname>OnCalendar=</varname></term>
+
+ <listitem><para>Defines realtime
+ (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
+ calendar event expressions. Otherwise,
+ the semantics are similar to
+ <varname>OnActiveSec=</varname> and
+ 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>
+ <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>
<listitem><para>The unit to activate
when this timer elapses. The argument is a
unit name, whose suffix is not
- <filename>.timer</filename>. If not
+ <literal>.timer</literal>. If not
specified, this value defaults to a
service that has the same name as the
timer unit, except for the
- suffix. (See above.) It is recommended,
+ suffix. (See above.) It is recommended
that the unit name that is activated
and the unit name of the timer unit
- are named identical, except for the
+ are named identically, except for the
suffix.</para></listitem>
</varlistentry>
</variablelist>
<refsect1>
<title>See Also</title>
<para>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.service</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-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
</para>
</refsect1>
~ianmdlvl / elogind.git / blobdiff