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e0cabd4b | 1 | <?xml version='1.0'?> <!--*-nxml-*--> |
e0cabd4b | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
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6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
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8 | This file is part of systemd. |
9 | ||
10 | Copyright 2010 Lennart Poettering | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
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13 | under the terms of the GNU Lesser General Public License as published by |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
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15 | (at your option) any later version. |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
5430f7f2 | 20 | Lesser General Public License for more details. |
e0cabd4b | 21 | |
5430f7f2 | 22 | You should have received a copy of the GNU Lesser General Public License |
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23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. |
24 | --> | |
25 | ||
26 | <refentry id="systemd.swap"> | |
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27 | <refentryinfo> |
28 | <title>systemd.swap</title> | |
29 | <productname>systemd</productname> | |
30 | ||
31 | <authorgroup> | |
32 | <author> | |
33 | <contrib>Developer</contrib> | |
34 | <firstname>Lennart</firstname> | |
35 | <surname>Poettering</surname> | |
36 | <email>lennart@poettering.net</email> | |
37 | </author> | |
38 | </authorgroup> | |
39 | </refentryinfo> | |
40 | ||
41 | <refmeta> | |
42 | <refentrytitle>systemd.swap</refentrytitle> | |
43 | <manvolnum>5</manvolnum> | |
44 | </refmeta> | |
45 | ||
46 | <refnamediv> | |
47 | <refname>systemd.swap</refname> | |
48 | <refpurpose>Swap unit configuration</refpurpose> | |
49 | </refnamediv> | |
50 | ||
51 | <refsynopsisdiv> | |
52 | <para><filename><replaceable>swap</replaceable>.swap</filename></para> | |
53 | </refsynopsisdiv> | |
54 | ||
55 | <refsect1> | |
56 | <title>Description</title> | |
57 | ||
58 | <para>A unit configuration file whose name ends in | |
59 | <literal>.swap</literal> encodes information about a swap device | |
60 | or file for memory paging controlled and supervised by | |
61 | systemd.</para> | |
62 | ||
63 | <para>This man page lists the configuration options specific to | |
64 | this unit type. See | |
65 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
66 | for the common options of all unit configuration files. The common | |
67 | configuration items are configured in the generic [Unit] and | |
68 | [Install] sections. The swap specific configuration options are | |
69 | configured in the [Swap] section.</para> | |
70 | ||
71 | <para>Additional options are listed in | |
72 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
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73 | which define the execution environment the <citerefentry |
74 | project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
3f2d1365 | 75 | program is executed in, in |
798d3a52 | 76 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
c629ff58 | 77 | which define the way these processes are |
c129bd5d | 78 | terminated, and in |
798d3a52 | 79 | <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
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80 | which configure resource control settings for these processes of the |
81 | unit.</para> | |
798d3a52 | 82 | |
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83 | <para>Swap units must be named after the devices or files they control. Example: the swap device <filename |
84 | noindex='true'>/dev/sda5</filename> must be configured in a unit file <filename>dev-sda5.swap</filename>. For | |
85 | details about the escaping logic used to convert a file system path to a unit name, see | |
86 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Note that swap | |
87 | units cannot be templated, nor is possible to add multiple names to a swap unit by creating additional symlinks to | |
88 | it.</para> | |
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89 | </refsect1> |
90 | ||
91 | <refsect1> | |
45f09f93 | 92 | <title>Implicit Dependencies</title> |
798d3a52 | 93 | |
45f09f93 | 94 | <para>The following dependencies are implicitly added:</para> |
798d3a52 | 95 | |
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96 | <itemizedlist> |
97 | <listitem><para>All swap units automatically get the | |
98 | <varname>BindsTo=</varname> and <varname>After=</varname> | |
99 | dependencies on the device units or the mount units of the files | |
100 | they are activated from.</para></listitem> | |
101 | </itemizedlist> | |
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102 | |
103 | <para>Additional implicit dependencies may be added as result of | |
104 | execution and resource control parameters as documented in | |
105 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
106 | and | |
107 | <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> | |
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108 | </refsect1> |
109 | ||
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110 | <refsect1> |
111 | <title>Default Dependencies</title> | |
112 | ||
113 | <para>The following dependencies are added unless <varname>DefaultDependencies=no</varname> is set:</para> | |
114 | ||
115 | <itemizedlist> | |
116 | <listitem><para>Swap units automatically acquire a <varname>Conflicts=</varname> and a | |
117 | <varname>Before=</varname> dependency on <filename>umount.target</filename> so that they are deactivated at | |
118 | shutdown as well as a <varname>Before=swap.target</varname> dependency.</para></listitem> | |
119 | </itemizedlist> | |
120 | </refsect1> | |
121 | ||
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122 | <refsect1> |
123 | <title><filename>fstab</filename></title> | |
124 | ||
125 | <para>Swap units may either be configured via unit files, or via | |
126 | <filename>/etc/fstab</filename> (see | |
3ba3a79d | 127 | <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
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128 | for details). Swaps listed in <filename>/etc/fstab</filename> will |
129 | be converted into native units dynamically at boot and when the | |
130 | configuration of the system manager is reloaded. See | |
131 | <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
132 | for details about the conversion.</para> | |
133 | ||
134 | <para>If a swap device or file is configured in both | |
135 | <filename>/etc/fstab</filename> and a unit file, the configuration | |
136 | in the latter takes precedence.</para> | |
137 | ||
b938cb90 | 138 | <para>When reading <filename>/etc/fstab</filename>, a few special |
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139 | options are understood by systemd which influence how dependencies |
140 | are created for swap units.</para> | |
141 | ||
142 | <variablelist class='fstab-options'> | |
143 | <varlistentry> | |
144 | <term><option>noauto</option></term> | |
145 | <term><option>auto</option></term> | |
146 | ||
b938cb90 | 147 | <listitem><para>With <option>noauto</option>, the swap unit |
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148 | will not be added as a dependency for |
149 | <filename>swap.target</filename>. This means that it will not | |
150 | be activated automatically during boot, unless it is pulled in | |
a8eaaee7 | 151 | by some other unit. The <option>auto</option> option has the |
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152 | opposite meaning and is the default.</para> |
153 | </listitem> | |
154 | </varlistentry> | |
155 | ||
156 | <varlistentry> | |
157 | <term><option>nofail</option></term> | |
158 | ||
b938cb90 | 159 | <listitem><para>With <option>nofail</option>, the swap unit |
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160 | will be only wanted, not required by |
161 | <filename>swap.target</filename>. This means that the boot | |
162 | will continue even if this swap device is not activated | |
163 | successfully.</para> | |
164 | </listitem> | |
165 | </varlistentry> | |
166 | </variablelist> | |
167 | </refsect1> | |
168 | ||
169 | <refsect1> | |
170 | <title>Options</title> | |
171 | ||
172 | <para>Swap files must include a [Swap] section, which carries | |
173 | information about the swap device it supervises. A number of | |
174 | options that may be used in this section are shared with other | |
175 | unit types. These options are documented in | |
176 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
177 | and | |
178 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
179 | The options specific to the [Swap] section of swap units are the | |
180 | following:</para> | |
181 | ||
182 | <variablelist class='unit-directives'> | |
183 | ||
184 | <varlistentry> | |
185 | <term><varname>What=</varname></term> | |
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186 | <listitem><para>Takes an absolute path of a device node or file to use for paging. See <citerefentry |
187 | project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry> for | |
188 | details. If this refers to a device node, a dependency on the respective device unit is automatically | |
189 | created. (See | |
190 | <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more | |
191 | information.) If this refers to a file, a dependency on the respective mount unit is automatically | |
192 | created. (See <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
193 | for more information.) This option is mandatory. Note that the usual specifier expansion is applied to this | |
194 | setting, literal percent characters should hence be written as <literal>%%</literal>.</para></listitem> | |
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195 | </varlistentry> |
196 | ||
197 | <varlistentry> | |
198 | <term><varname>Priority=</varname></term> | |
199 | ||
200 | <listitem><para>Swap priority to use when activating the swap | |
201 | device or file. This takes an integer. This setting is | |
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202 | optional and ignored when the priority is set by <option>pri=</option> in the |
203 | <varname>Options=</varname> key.</para></listitem> | |
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204 | </varlistentry> |
205 | ||
206 | <varlistentry> | |
207 | <term><varname>Options=</varname></term> | |
208 | ||
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209 | <listitem><para>May contain an option string for the swap device. This may be used for controlling discard |
210 | options among other functionality, if the swap backing device supports the discard or trim operation. (See | |
3ba3a79d | 211 | <citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
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212 | for more information.) Note that the usual specifier expansion is applied to this setting, literal percent |
213 | characters should hence be written as <literal>%%</literal>.</para></listitem> | |
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214 | </varlistentry> |
215 | ||
216 | <varlistentry> | |
217 | <term><varname>TimeoutSec=</varname></term> | |
218 | <listitem><para>Configures the time to wait for the swapon | |
219 | command to finish. If a command does not exit within the | |
220 | configured time, the swap will be considered failed and be | |
221 | shut down again. All commands still running will be terminated | |
222 | forcibly via <constant>SIGTERM</constant>, and after another | |
223 | delay of this time with <constant>SIGKILL</constant>. (See | |
224 | <option>KillMode=</option> in | |
225 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.) | |
226 | Takes a unit-less value in seconds, or a time span value such | |
227 | as "5min 20s". Pass <literal>0</literal> to disable the | |
228 | timeout logic. Defaults to | |
229 | <varname>DefaultTimeoutStartSec=</varname> from the manager | |
230 | configuration file (see | |
231 | <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>). | |
232 | </para></listitem> | |
233 | </varlistentry> | |
234 | </variablelist> | |
235 | ||
236 | <para>Check | |
237 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
238 | and | |
239 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
240 | for more settings.</para> | |
241 | </refsect1> | |
242 | ||
243 | <refsect1> | |
244 | <title>See Also</title> | |
245 | <para> | |
246 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
247 | <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
248 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
249 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
250 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
251 | <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
252 | <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
253 | <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
3ba3a79d | 254 | <citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
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255 | <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
256 | <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
257 | </para> | |
258 | </refsect1> | |
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259 | |
260 | </refentry> |