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<?xml version='1.0'?> <!--*-nxml-*-->
<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2010 Lennart Poettering
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<refentry id="systemd.timer">
<refentryinfo>
<title>systemd.timer</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.timer</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.timer</refname>
<refpurpose>Timer unit configuration</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename><replaceable>timer</replaceable>.timer</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>A unit configuration file whose name ends in
<literal>.timer</literal> encodes information about
a timer controlled and supervised by systemd, for
timer-based activation.</para>
<para>This man page lists the configuration options
specific to this unit type. See
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for the common options of all unit configuration
files. The common configuration items are configured
in the generic [Unit] and [Install] sections. The
timer specific configuration options are configured in
the [Timer] section.</para>
<para>For each timer file, a matching unit file must
exist, describing the unit to activate when the timer
elapses. By default, a service by the same name as the
timer (except for the suffix) is activated. Example: a
timer file <filename>foo.timer</filename> activates a
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>, all timer units will
implicitly have dependencies of type
<varname>Conflicts=</varname> and
<varname>Before=</varname> on
<filename>shutdown.target</filename> to ensure that
they are stopped cleanly prior to system shutdown.
Timer units with at least one
<varname>OnCalendar=</varname> directive will have an
additional <varname>After=</varname> dependency on
<filename>timer-sync.target</filename> to avoid
being started before the system clock has been
correctly set. Only timer units involved with early
boot or late system shutdown should disable the
<varname>DefaultDependencies=</varname> option.</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>Timer files must include a [Timer] section,
which carries information about the timer it
defines. The options specific to the [Timer] section
of timer units are the following:</para>
<variablelist class='unit-directives'>
<varlistentry>
<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 monotonic timers
relative to different starting points:
<varname>OnActiveSec=</varname> defines a
timer relative to the moment the timer
itself is
activated. <varname>OnBootSec=</varname>
defines a timer relative to when the
machine was booted
up. <varname>OnStartupSec=</varname>
defines a timer relative to when
systemd was first
started. <varname>OnUnitActiveSec=</varname>
defines a timer relative to when the
unit the timer is activating was last
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>OnBootSec=</varname> and
<varname>OnUnitActiveSec=</varname>, it is
possible to define a timer that
elapses in regular intervals and
activates a specific service each
time.</para>
<para>The arguments to the directives
are time spans configured in
seconds. Example: "OnBootSec=50" means
50s after boot-up. The argument may
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
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
<para>If a timer configured with
<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>
<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
<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
that the unit name that is activated
and the unit name of the timer unit
are named identically, except for the
suffix.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Persistent=</varname></term>
<listitem><para>Takes a boolean
argument. If true, the time when the
service unit was last triggered is
stored on disk. When the timer is
activated, the service unit is
triggered immediately if it would have
been triggered at least once during
the time when the timer was inactive.
This is useful to catch up on missed
runs of the service when the machine
was off. Note that this setting only
has an effect on timers configured
with <varname>OnCalendar=</varname>.
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>WakeSystem=</varname></term>
<listitem><para>Takes a boolean
argument. If true, an elapsing timer
will cause the system to resume 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></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</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-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
|
