312 lines
17 KiB
XML
312 lines
17 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="systemd.timer">
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<refentryinfo>
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<title>systemd.timer</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd.timer</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd.timer</refname>
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<refpurpose>Timer unit configuration</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename><replaceable>timer</replaceable>.timer</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>A unit configuration file whose name ends in
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<literal>.timer</literal> encodes information about
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a timer controlled and supervised by systemd, for
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timer-based activation.</para>
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<para>This man page lists the configuration options
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specific to this unit type. See
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for the common options of all unit configuration
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files. The common configuration items are configured
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in the generic [Unit] and [Install] sections. The
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timer specific configuration options are configured in
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the [Timer] section.</para>
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<para>For each timer file, a matching unit file must
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exist, describing the unit to activate when the timer
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elapses. By default, a service by the same name as the
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timer (except for the suffix) is activated. Example: a
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timer file <filename>foo.timer</filename> activates a
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matching service <filename>foo.service</filename>. The
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unit to activate may be controlled by
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<varname>Unit=</varname> (see below).</para>
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<para>Unless <varname>DefaultDependencies=</varname>
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is set to <option>false</option>, all timer units will
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implicitly have dependencies of type
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<varname>Conflicts=</varname> and
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<varname>Before=</varname> on
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<filename>shutdown.target</filename> to ensure that
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they are stopped cleanly prior to system shutdown.
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Timer units with at least one
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<varname>OnCalendar=</varname> directive will have an
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additional <varname>After=</varname> dependency on
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<filename>timer-sync.target</filename> to avoid
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being started before the system clock has been
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correctly set. Only timer units involved with early
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boot or late system shutdown should disable the
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<varname>DefaultDependencies=</varname> option.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>Timer files must include a [Timer] section,
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which carries information about the timer it
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defines. The options specific to the [Timer] section
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of timer units are the following:</para>
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<variablelist class='unit-directives'>
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<varlistentry>
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<term><varname>OnActiveSec=</varname></term>
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<term><varname>OnBootSec=</varname></term>
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<term><varname>OnStartupSec=</varname></term>
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<term><varname>OnUnitActiveSec=</varname></term>
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<term><varname>OnUnitInactiveSec=</varname></term>
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<listitem><para>Defines monotonic timers
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relative to different starting points:
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<varname>OnActiveSec=</varname> defines a
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timer relative to the moment the timer
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itself is
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activated. <varname>OnBootSec=</varname>
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defines a timer relative to when the
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machine was booted
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up. <varname>OnStartupSec=</varname>
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defines a timer relative to when
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systemd was first
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started. <varname>OnUnitActiveSec=</varname>
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defines a timer relative to when the
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unit the timer is activating was last
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activated. <varname>OnUnitInactiveSec=</varname>
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defines a timer relative to when the
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unit the timer is activating was last
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deactivated.</para>
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<para>Multiple directives may be
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combined of the same and of different
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types. For example, by combining
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<varname>OnBootSec=</varname> and
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<varname>OnUnitActiveSec=</varname>, it is
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possible to define a timer that
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elapses in regular intervals and
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activates a specific service each
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time.</para>
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<para>The arguments to the directives
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are time spans configured in
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seconds. Example: "OnBootSec=50" means
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50s after boot-up. The argument may
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also include time units. Example:
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"OnBootSec=5h 30min" means 5 hours and
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30 minutes after boot-up. For details
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about the syntax of time spans, see
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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<para>If a timer configured with
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<varname>OnBootSec=</varname> or
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<varname>OnStartupSec=</varname> is
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already in the past when the timer
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unit is activated, it will immediately
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elapse and the configured unit is
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started. This is not the case for
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timers defined in the other
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directives.</para>
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<para>These are monotonic timers,
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independent of wall-clock time and timezones. If the
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computer is temporarily suspended, the
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monotonic clock stops too.</para>
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<para>If the empty string is assigned
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to any of these options, the list of
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timers is reset, and all prior
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assignments will have no
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effect.</para>
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<para>Note that timers do not
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necessarily expire at the precise
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time configured with these settings,
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as they are subject to the
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<varname>AccuracySec=</varname>
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setting below.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>OnCalendar=</varname></term>
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<listitem><para>Defines realtime
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(i.e. wallclock) timers with calendar
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event expressions. See
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<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for more information on the syntax of
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calendar event expressions. Otherwise,
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the semantics are similar to
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<varname>OnActiveSec=</varname> and
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related settings.</para>
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<para>Note that timers do not
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necessarily expire at the precise
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time configured with this setting,
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as it is subject to the
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<varname>AccuracySec=</varname>
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setting below.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>AccuracySec=</varname></term>
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<listitem><para>Specify the accuracy
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the timer shall elapse with. Defaults
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to 1min. The timer is scheduled to
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elapse within a time window starting
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with the time specified in
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<varname>OnCalendar=</varname>,
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<varname>OnActiveSec=</varname>,
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<varname>OnBootSec=</varname>,
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<varname>OnStartupSec=</varname>,
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<varname>OnUnitActiveSec=</varname> or
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<varname>OnUnitInactiveSec=</varname>
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and ending the time configured with
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<varname>AccuracySec=</varname>
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later. Within this time window, the
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expiry time will be placed at a
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host-specific, randomized but stable
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position that is synchronized between
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all local timer units. This is done in
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order to distribute the wake-up time
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in networked installations, as well as
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optimizing power consumption to
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suppress unnecessary CPU wake-ups. To
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get best accuracy, set this option to
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1us. Note that the timer is still
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subject to the timer slack configured
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via
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<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>'s
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<varname>TimerSlackNSec=</varname>
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setting. See
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<citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details. To optimize power
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consumption, make sure to set this
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value as high as possible and as low
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as necessary.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>Unit=</varname></term>
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<listitem><para>The unit to activate
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when this timer elapses. The argument is a
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unit name, whose suffix is not
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<literal>.timer</literal>. If not
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specified, this value defaults to a
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service that has the same name as the
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timer unit, except for the
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suffix. (See above.) It is recommended
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that the unit name that is activated
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and the unit name of the timer unit
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are named identically, except for the
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suffix.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>Persistent=</varname></term>
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<listitem><para>Takes a boolean
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argument. If true, the time when the
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service unit was last triggered is
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stored on disk. When the timer is
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activated, the service unit is
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triggered immediately if it would have
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been triggered at least once during
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the time when the timer was inactive.
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This is useful to catch up on missed
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runs of the service when the machine
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was off. Note that this setting only
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has an effect on timers configured
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with <varname>OnCalendar=</varname>.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>WakeSystem=</varname></term>
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<listitem><para>Takes a boolean
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argument. If true, an elapsing timer
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will cause the system to resume from
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suspend, should it be suspended and if
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the system supports this. Note that
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this option will only make sure the
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system resumes on the appropriate
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times, it will not take care of
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suspending it again after any work
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that is to be done is
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finished. Defaults to
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<varname>false</varname>.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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