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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+
+<refentry id="systemd.swap" xmlns:xi="http://www.w3.org/2001/XInclude">
+ <refentryinfo>
+ <title>systemd.swap</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>systemd.swap</refentrytitle>
+ <manvolnum>5</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>systemd.swap</refname>
+ <refpurpose>Swap unit configuration</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <para><filename><replaceable>swap</replaceable>.swap</filename></para>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>A unit configuration file whose name ends in
+ <literal>.swap</literal> encodes information about a swap device
+ or file for memory paging controlled and supervised by
+ systemd.</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 swap specific configuration options are
+ configured in the [Swap] section.</para>
+
+ <para>Additional options are listed in
+ <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ which define the execution environment the <citerefentry
+ project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ program is executed in, in
+ <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ which define the way these processes are
+ terminated, and in
+ <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ which configure resource control settings for these processes of the
+ unit.</para>
+
+ <para>Swap units must be named after the devices or files they control. Example: the swap device <filename
+ index="false">/dev/sda5</filename> must be configured in a unit file <filename>dev-sda5.swap</filename>. For
+ details about the escaping logic used to convert a file system path to a unit name, see
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Note that swap
+ units cannot be templated, nor is possible to add multiple names to a swap unit by creating additional symlinks to
+ it.</para>
+
+ <para>Note that swap support on Linux is privileged, swap units are hence only available in the system
+ service manager (and root's user service manager), but not in unprivileged user's service manager.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Automatic Dependencies</title>
+
+ <refsect2>
+ <title>Implicit Dependencies</title>
+
+ <para>The following dependencies are implicitly added:</para>
+
+ <itemizedlist>
+ <listitem><para>All swap units automatically get the
+ <varname>BindsTo=</varname> and <varname>After=</varname>
+ dependencies on the device units or the mount units of the files
+ they are activated from.</para></listitem>
+ </itemizedlist>
+
+ <para>Additional implicit dependencies may be added as result of
+ execution and resource control parameters as documented in
+ <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ and
+ <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+ </refsect2>
+
+ <refsect2>
+ <title>Default Dependencies</title>
+
+ <para>The following dependencies are added unless <varname>DefaultDependencies=no</varname> is set:</para>
+
+ <itemizedlist>
+ <listitem><para>Swap units automatically acquire a <varname>Conflicts=</varname> and a
+ <varname>Before=</varname> dependency on <filename>umount.target</filename> so that they are deactivated at
+ shutdown as well as a <varname>Before=swap.target</varname> dependency.</para></listitem>
+ </itemizedlist>
+ </refsect2>
+ </refsect1>
+
+ <refsect1>
+ <title><filename>fstab</filename></title>
+
+ <para>Swap units may either be configured via unit files, or via
+ <filename>/etc/fstab</filename> (see
+ <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details). Swaps listed in <filename>/etc/fstab</filename> will
+ be converted into native units dynamically at boot and when the
+ configuration of the system manager is reloaded. See
+ <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ for details about the conversion.</para>
+
+ <para>If a swap device or file is configured in both
+ <filename>/etc/fstab</filename> and a unit file, the configuration
+ in the latter takes precedence.</para>
+
+ <para>When reading <filename>/etc/fstab</filename>, a few special
+ options are understood by systemd which influence how dependencies
+ are created for swap units.</para>
+
+ <variablelist class='fstab-options'>
+ <varlistentry>
+ <term><option>noauto</option></term>
+ <term><option>auto</option></term>
+
+ <listitem><para>With <option>noauto</option>, the swap unit
+ will not be added as a dependency for
+ <filename>swap.target</filename>. This means that it will not
+ be activated automatically during boot, unless it is pulled in
+ by some other unit. The <option>auto</option> option has the
+ opposite meaning and is the default.</para>
+
+ <xi:include href="version-info.xml" xpointer="v218"/>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>nofail</option></term>
+
+ <listitem><para>With <option>nofail</option>, the swap unit
+ will be only wanted, not required by
+ <filename>swap.target</filename>. This means that the boot
+ will continue even if this swap device is not activated
+ successfully.</para>
+
+ <xi:include href="version-info.xml" xpointer="v218"/>
+ </listitem>
+ </varlistentry>
+
+ <xi:include href="systemd.mount.xml" xpointer="device-timeout" />
+
+ <varlistentry>
+ <term><option>x-systemd.makefs</option></term>
+
+ <listitem><para>The swap structure will be initialized on the device. If the device is not
+ "empty", i.e. it contains any signature, the operation will be skipped. It is hence expected
+ that this option remains set even after the device has been initialized.</para>
+
+ <para>Note that this option can only be used in <filename>/etc/fstab</filename>, and will be
+ ignored when part of the <varname>Options=</varname> setting in a unit file.</para>
+
+ <para>See
+ <citerefentry><refentrytitle>systemd-mkswap@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ and the discussion of
+ <citerefentry project='man-pages'><refentrytitle>wipefs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ in <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </para>
+
+ <xi:include href="version-info.xml" xpointer="v240"/></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Options</title>
+
+ <para>Swap unit files may include [Unit] and [Install] sections, which are described in
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </para>
+
+ <para>Swap unit files must include a [Swap] section, which carries
+ information about the swap device it supervises. A number of
+ options that may be used in this section are shared with other
+ unit types. These options are documented in
+ <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ and
+ <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ The options specific to the [Swap] section of swap units are the
+ following:</para>
+
+ <variablelist class='unit-directives'>
+
+ <varlistentry>
+ <term><varname>What=</varname></term>
+ <listitem><para>Takes an absolute path of a device node or file to use for paging. See <citerefentry
+ project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry> for
+ details. If this refers to a device node, a dependency on the respective device unit is automatically
+ created. (See
+ <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for more information.) If this refers to a file, a dependency on the respective mount unit is
+ automatically created. (See
+ <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
+ more information.) This option is mandatory. Note that the usual specifier expansion is applied to
+ this setting, literal percent characters should hence be written as
+ <literal class='specifiers'>%%</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>Priority=</varname></term>
+
+ <listitem><para>Swap priority to use when activating the swap
+ device or file. This takes an integer. This setting is
+ optional and ignored when the priority is set by <option>pri=</option> in the
+ <varname>Options=</varname> key.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>Options=</varname></term>
+
+ <listitem><para>May contain an option string for the swap device. This may be used for controlling discard
+ options among other functionality, if the swap backing device supports the discard or trim operation. (See
+ <citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ for more information.) Note that the usual specifier expansion is applied to this setting, literal percent
+ characters should hence be written as <literal>%%</literal>.</para>
+
+ <xi:include href="version-info.xml" xpointer="v217"/></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>TimeoutSec=</varname></term>
+ <listitem><para>Configures the time to wait for the swapon
+ command to finish. If a command does not exit within the
+ configured time, the swap will be considered failed and be
+ shut down again. All commands still running will be terminated
+ forcibly via <constant>SIGTERM</constant>, and after another
+ delay of this time with <constant>SIGKILL</constant>. (See
+ <option>KillMode=</option> in
+ <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.)
+ Takes a unit-less value in seconds, or a time span value such
+ as "5min 20s". Pass <literal>0</literal> to disable the
+ timeout logic. Defaults to
+ <varname>DefaultTimeoutStartSec=</varname> from the manager
+ configuration file (see
+ <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+
+ <xi:include href="systemd.service.xml" xpointer="shared-unit-options" />
+ </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-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>