1
1
mirror of https://github.com/systemd/systemd-stable.git synced 2024-12-23 17:34:00 +03:00
systemd-stable/man/systemd.timer.xml
Tom Gundersen 12b42c7667 man: revert dynamic paths for split-usr setups
This did not really work out as we had hoped. Trying to do this upstream
introduced several problems that probably makes it better suited as a
downstream patch after all. At any rate, it is not releaseable in the
current state, so we at least need to revert this before the release.

 * by adjusting the path to binaries, but not do the same thing to the
   search path we end up with inconsistent man-pages. Adjusting the search
   path too would be quite messy, and it is not at all obvious that this is
   worth the effort, but at any rate it would have to be done before we
   could ship this.

 * this means that distributed man-pages does not make sense as they depend
   on config options, and for better or worse we are still distributing
   man pages, so that is something that definitely needs sorting out before
   we could ship with this patch.

 * we have long held that split-usr is only minimally supported in order
   to boot, and something we hope will eventually go away. So before we start
   adding even more magic/effort in order to make this work nicely, we should
   probably question if it makes sense at all.
2015-06-18 19:47:44 +02:00

254 lines
11 KiB
XML

<?xml version='1.0'?> <!--*-nxml-*-->
<!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
systemd is free software; you can redistribute it and/or modify it
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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<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>