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5607d856b8
systemd stops adding automatic dependencies on swap.target to swap units. If a dependency is required, it has to be added by unit configuration. fstab-generator did that already, except that now it is modified to create a Requires or Wants type dependency, depending on whether nofail is specified in /etc/fstab. This makes .swap units obey the nofail/noauto options more or less the same as .mount units. Documentation is extended to clarify that, and to make systemd.mount(5) and system.swap(5) more similar. The gist is not changed, because current behaviour actually matches existing documentation. https://bugs.freedesktop.org/show_bug.cgi?id=86488
263 lines
14 KiB
XML
263 lines
14 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.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
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swap device or file for memory paging controlled and
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supervised by systemd.</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 swap
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specific configuration options are configured in the
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[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
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<citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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binary is executed in, and in
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<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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which define the way the 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 the
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processes of the service.</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
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details about the escaping logic used to convert a
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file system path to a unit name, see
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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<para>All swap units automatically get the appropriate
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dependencies on the devices or on the mount points
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of the files they are activated from.</para>
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<para>Swap units with
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<varname>DefaultDependencies=</varname> enabled
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implicitly acquire a conflicting dependency to
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<filename>umount.target</filename> so that they are
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deactivated at shutdown.</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
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files, or via <filename>/etc/fstab</filename> (see
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<citerefentry><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details). Swaps listed in
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<filename>/etc/fstab</filename> will be converted into
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native units dynamically at boot and when the
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configuration of the system manager is
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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
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configuration in the latter takes precedence.</para>
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<para>When reading <filename>/etc/fstab</filename> a
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few special options are understood by systemd which
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influence how dependencies are created for swap
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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
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swap unit will not be added as a dependency for
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<filename>swap.target</filename>. This means that
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it will not be activated automatically during
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boot, unless it is pulled in by some other
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unit. Option <option>auto</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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<term><option>fail</option></term>
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<listitem><para>With <option>nofail</option> the
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swap unit will be only wanted, not required by
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<filename>swap.target</filename>. This means that
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the boot will continue even if this swap device is
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not activated successfully. Option
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<option>fail</option> has the opposite meaning and
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is the default.</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
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carries information about the swap device it
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supervises. A number of options that may be used in
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this section are shared with other unit types. These
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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>. The
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options specific to the [Swap] section of swap units
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are the 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
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of a device node or file to use for
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paging. See
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<citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for details. If this refers to a
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device node, a dependency on the
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respective device unit is
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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
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to a file, a dependency on the
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respective mount unit is automatically
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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
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when activating the swap device or
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file. This takes an integer. This
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setting is optional.</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
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string for the swap device. This may
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be used for controlling discard
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options among other functionality, if
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the swap backing device supports the
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discard or trim operation. (See
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<citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for more information.)
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</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
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wait for the swapon command to
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finish. If a command does not exit
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within the configured time, the swap
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will be considered failed and be shut
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down again. All commands still running
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will be terminated forcibly via
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<constant>SIGTERM</constant>, and after another delay of
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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
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a time span value such as "5min
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20s". Pass <literal>0</literal> to disable the timeout
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logic. Defaults to <varname>DefaultTimeoutStartSec=</varname> from the
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manager configuration file
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(see <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><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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