<?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" [
-<!ENTITY % entities SYSTEM "custom-entities.ent" >
-%entities;
-]>
+ "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/>.
+ SPDX-License-Identifier: LGPL-2.1+
-->
<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>
<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
+ 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 the processes are terminated, and in
+ 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 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>
+ 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>. 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>
+ </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>
<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
+ <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>
<term><option>noauto</option></term>
<term><option>auto</option></term>
- <listitem><para>With <option>noauto</option> the swap unit
+ <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
+ 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
+ <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
<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>
+ <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>%%</literal>.</para></listitem>
</varlistentry>
<varlistentry>
<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>
+ 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
+ <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>
+ 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></listitem>
</varlistentry>
<varlistentry>
projects / thirdparty / systemd.git / blobdiff