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<?xml version='1.0'?> <!--*-nxml-*-->
<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
<!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
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(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
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You should have received a copy of the GNU Lesser General Public License
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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><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><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><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.</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><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><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>
|
