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<?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.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, in
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
which define the way the 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 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>
</refsect1>
<refsect1>
<title>Automatic Dependencies</title>
<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>
<para>Swap units with <varname>DefaultDependencies=</varname>
enabled implicitly acquire a <varname>Conflicts=</varname> and an
<varname>After=</varname> dependency on
<filename>umount.target</filename> so that they are deactivated at
shutdown, unless <varname>DefaultDependencies=no</varname> is
specified.</para>
<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>
</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>
</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 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.) </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>
|
