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<refentry id="systemd.swap">

<refentryinfo>

<title>systemd.swap</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.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>

binary is executed in, and in

<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,

which define the way the processes are terminated, and in

<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,

which configure resource control settings for the processes of the

service.</para>

<para>Swap units must be named after the devices

or files they control. Example: the swap device

<filename noindex='true'>/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>.</para>

<para>All swap units automatically get the appropriate

dependencies on the devices or on the mount points of the files

they are activated from.</para>

<para>Swap units with <varname>DefaultDependencies=</varname>

enabled implicitly acquire a conflicting dependency to

<filename>umount.target</filename> so that they are deactivated at

shutdown.</para>

</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. Option <option>auto</option> has the

opposite meaning and is the default.</para>

</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>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>Options</title>

<para>Swap 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.</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 priority is set by <option>pri=</option> in the

<varname>Options=</varname> option.</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.) </para></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>

<para>Check

<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>

and

<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>

for more settings.</para>

</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.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>