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For all units ensure there's an "Automatic Dependencies" section in the man page, and explain which dependencies are automatically added in all cases, and which ones are added on top if DefaultDependencies=yes is set. This is also done for systemd.exec(5), systemd.resource-control(5) and systemd.unit(5) as these pages describe common behaviour of various unit types.
254 lines
11 KiB
XML
254 lines
11 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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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.swap">
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<refentryinfo>
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<title>systemd.swap</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.swap</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd.swap</refname>
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<refpurpose>Swap unit configuration</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename><replaceable>swap</replaceable>.swap</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>.swap</literal> encodes information about a swap device
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or file for memory paging controlled and supervised by
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systemd.</para>
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<para>This man page lists the configuration options specific to
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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 files. The common
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configuration items are configured in the generic [Unit] and
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[Install] sections. The swap specific configuration options are
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configured in the [Swap] section.</para>
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<para>Additional options are listed in
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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which define the execution environment the <citerefentry
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project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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binary is executed in, in
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<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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which define the way the these processes are
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terminated, and in
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<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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which configure resource control settings for these processes of the
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unit.</para>
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<para>Swap units must be named after the devices
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or files they control. Example: the swap device
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<filename noindex='true'>/dev/sda5</filename> must be configured in a
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unit file <filename>dev-sda5.swap</filename>. For details about
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the escaping logic used to convert a file system path to a unit
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name, see
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title>Automatic Dependencies</title>
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<para>All swap units automatically get the
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<varname>BindsTo=</varname> and <varname>After=</varname>
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dependencies on the device units or the mount units of the files
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they are activated from.</para>
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<para>Swap units with <varname>DefaultDependencies=</varname>
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enabled implicitly acquire a <varname>Conflicts=</varname> and an
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<varname>After=</varname> dependency on
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<filename>umount.target</filename> so that they are deactivated at
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shutdown, unless <varname>DefaultDependencies=no</varname> is
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specified.</para>
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<para>Additional implicit dependencies may be added as result of
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execution and resource control parameters as documented in
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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and
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<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title><filename>fstab</filename></title>
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<para>Swap units may either be configured via unit files, or via
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<filename>/etc/fstab</filename> (see
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<citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details). Swaps listed in <filename>/etc/fstab</filename> will
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be converted into native units dynamically at boot and when the
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configuration of the system manager is reloaded. See
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<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for details about the conversion.</para>
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<para>If a swap device or file is configured in both
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<filename>/etc/fstab</filename> and a unit file, the configuration
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in the latter takes precedence.</para>
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<para>When reading <filename>/etc/fstab</filename>, a few special
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options are understood by systemd which influence how dependencies
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are created for swap units.</para>
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<variablelist class='fstab-options'>
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<varlistentry>
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<term><option>noauto</option></term>
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<term><option>auto</option></term>
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<listitem><para>With <option>noauto</option>, the swap unit
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will not be added as a dependency for
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<filename>swap.target</filename>. This means that it will not
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be activated automatically during boot, unless it is pulled in
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by some other unit. The <option>auto</option> option has the
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opposite meaning and is the default.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>nofail</option></term>
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<listitem><para>With <option>nofail</option>, the swap unit
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will be only wanted, not required by
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<filename>swap.target</filename>. This means that the boot
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will continue even if this swap device is not activated
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successfully.</para>
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</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>Options</title>
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<para>Swap files must include a [Swap] section, which carries
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information about the swap device it supervises. A number of
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options that may be used in this section are shared with other
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unit types. These options are documented in
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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and
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<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
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The options specific to the [Swap] section of swap units are the
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following:</para>
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<variablelist class='unit-directives'>
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<varlistentry>
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<term><varname>What=</varname></term>
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<listitem><para>Takes an absolute path of a device node or
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file to use for paging. See
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<citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for details. If this refers to a device node, a dependency on
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the respective device unit is automatically created. (See
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<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for more information.) If this refers to a file, a dependency
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on the respective mount unit is automatically created. (See
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<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for more information.) This option is
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mandatory.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>Priority=</varname></term>
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<listitem><para>Swap priority to use when activating the swap
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device or file. This takes an integer. This setting is
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optional and ignored when the priority is set by <option>pri=</option> in the
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<varname>Options=</varname> key.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>Options=</varname></term>
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<listitem><para>May contain an option string for the swap
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device. This may be used for controlling discard options among
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other functionality, if the swap backing device supports the
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discard or trim operation. (See
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<citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for more information.) </para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>TimeoutSec=</varname></term>
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<listitem><para>Configures the time to wait for the swapon
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command to finish. If a command does not exit within the
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configured time, the swap will be considered failed and be
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shut down again. All commands still running will be terminated
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forcibly via <constant>SIGTERM</constant>, and after another
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delay of this time with <constant>SIGKILL</constant>. (See
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<option>KillMode=</option> in
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<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.)
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Takes a unit-less value in seconds, or a time span value such
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as "5min 20s". Pass <literal>0</literal> to disable the
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timeout logic. Defaults to
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<varname>DefaultTimeoutStartSec=</varname> from the manager
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configuration file (see
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<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
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</para></listitem>
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</varlistentry>
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</variablelist>
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<para>Check
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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and
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<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for more settings.</para>
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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>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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