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e0cabd4b | 1 | <?xml version='1.0'?> <!--*-nxml-*--> |
3a54a157 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
eea10b26 | 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> |
db9ecf05 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
e0cabd4b | 5 | |
d8e1613e | 6 | <refentry id="systemd.swap" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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7 | <refentryinfo> |
8 | <title>systemd.swap</title> | |
9 | <productname>systemd</productname> | |
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10 | </refentryinfo> |
11 | ||
12 | <refmeta> | |
13 | <refentrytitle>systemd.swap</refentrytitle> | |
14 | <manvolnum>5</manvolnum> | |
15 | </refmeta> | |
16 | ||
17 | <refnamediv> | |
18 | <refname>systemd.swap</refname> | |
19 | <refpurpose>Swap unit configuration</refpurpose> | |
20 | </refnamediv> | |
21 | ||
22 | <refsynopsisdiv> | |
23 | <para><filename><replaceable>swap</replaceable>.swap</filename></para> | |
24 | </refsynopsisdiv> | |
25 | ||
26 | <refsect1> | |
27 | <title>Description</title> | |
28 | ||
29 | <para>A unit configuration file whose name ends in | |
30 | <literal>.swap</literal> encodes information about a swap device | |
31 | or file for memory paging controlled and supervised by | |
32 | systemd.</para> | |
33 | ||
34 | <para>This man page lists the configuration options specific to | |
35 | this unit type. See | |
36 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
37 | for the common options of all unit configuration files. The common | |
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38 | configuration items are configured in the generic [Unit] and |
39 | [Install] sections. The swap specific configuration options are | |
40 | configured in the [Swap] section.</para> | |
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41 | |
42 | <para>Additional options are listed in | |
43 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
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44 | which define the execution environment the <citerefentry |
45 | project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
3f2d1365 | 46 | program is executed in, in |
798d3a52 | 47 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
c629ff58 | 48 | which define the way these processes are |
c129bd5d | 49 | terminated, and in |
798d3a52 | 50 | <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
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51 | which configure resource control settings for these processes of the |
52 | unit.</para> | |
798d3a52 | 53 | |
f4bf8d2f | 54 | <para>Swap units must be named after the devices or files they control. Example: the swap device <filename |
b0343f8c | 55 | index="false">/dev/sda5</filename> must be configured in a unit file <filename>dev-sda5.swap</filename>. For |
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56 | details about the escaping logic used to convert a file system path to a unit name, see |
57 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Note that swap | |
58 | units cannot be templated, nor is possible to add multiple names to a swap unit by creating additional symlinks to | |
59 | it.</para> | |
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60 | |
61 | <para>Note that swap support on Linux is privileged, swap units are hence only available in the system | |
62 | service manager (and root's user service manager), but not in unprivileged user's service manager.</para> | |
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63 | </refsect1> |
64 | ||
65 | <refsect1> | |
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66 | <title>Automatic Dependencies</title> |
67 | ||
68 | <refsect2> | |
69 | <title>Implicit Dependencies</title> | |
70 | ||
71 | <para>The following dependencies are implicitly added:</para> | |
72 | ||
73 | <itemizedlist> | |
74 | <listitem><para>All swap units automatically get the | |
75 | <varname>BindsTo=</varname> and <varname>After=</varname> | |
76 | dependencies on the device units or the mount units of the files | |
77 | they are activated from.</para></listitem> | |
78 | </itemizedlist> | |
79 | ||
80 | <para>Additional implicit dependencies may be added as result of | |
81 | execution and resource control parameters as documented in | |
82 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
83 | and | |
84 | <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> | |
85 | </refsect2> | |
86 | ||
87 | <refsect2> | |
88 | <title>Default Dependencies</title> | |
89 | ||
90 | <para>The following dependencies are added unless <varname>DefaultDependencies=no</varname> is set:</para> | |
91 | ||
92 | <itemizedlist> | |
93 | <listitem><para>Swap units automatically acquire a <varname>Conflicts=</varname> and a | |
94 | <varname>Before=</varname> dependency on <filename>umount.target</filename> so that they are deactivated at | |
95 | shutdown as well as a <varname>Before=swap.target</varname> dependency.</para></listitem> | |
96 | </itemizedlist> | |
97 | </refsect2> | |
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98 | </refsect1> |
99 | ||
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100 | <refsect1> |
101 | <title><filename>fstab</filename></title> | |
102 | ||
103 | <para>Swap units may either be configured via unit files, or via | |
104 | <filename>/etc/fstab</filename> (see | |
3ba3a79d | 105 | <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
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106 | for details). Swaps listed in <filename>/etc/fstab</filename> will |
107 | be converted into native units dynamically at boot and when the | |
108 | configuration of the system manager is reloaded. See | |
109 | <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
110 | for details about the conversion.</para> | |
111 | ||
112 | <para>If a swap device or file is configured in both | |
113 | <filename>/etc/fstab</filename> and a unit file, the configuration | |
114 | in the latter takes precedence.</para> | |
115 | ||
b938cb90 | 116 | <para>When reading <filename>/etc/fstab</filename>, a few special |
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117 | options are understood by systemd which influence how dependencies |
118 | are created for swap units.</para> | |
119 | ||
120 | <variablelist class='fstab-options'> | |
121 | <varlistentry> | |
122 | <term><option>noauto</option></term> | |
123 | <term><option>auto</option></term> | |
124 | ||
b938cb90 | 125 | <listitem><para>With <option>noauto</option>, the swap unit |
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126 | will not be added as a dependency for |
127 | <filename>swap.target</filename>. This means that it will not | |
128 | be activated automatically during boot, unless it is pulled in | |
a8eaaee7 | 129 | by some other unit. The <option>auto</option> option has the |
798d3a52 | 130 | opposite meaning and is the default.</para> |
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131 | |
132 | <xi:include href="version-info.xml" xpointer="v218"/> | |
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133 | </listitem> |
134 | </varlistentry> | |
135 | ||
136 | <varlistentry> | |
137 | <term><option>nofail</option></term> | |
138 | ||
b938cb90 | 139 | <listitem><para>With <option>nofail</option>, the swap unit |
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140 | will be only wanted, not required by |
141 | <filename>swap.target</filename>. This means that the boot | |
142 | will continue even if this swap device is not activated | |
143 | successfully.</para> | |
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144 | |
145 | <xi:include href="version-info.xml" xpointer="v218"/> | |
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146 | </listitem> |
147 | </varlistentry> | |
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148 | |
149 | <xi:include href="systemd.mount.xml" xpointer="device-timeout" /> | |
150 | ||
151 | <varlistentry> | |
152 | <term><option>x-systemd.makefs</option></term> | |
153 | ||
154 | <listitem><para>The swap structure will be initialized on the device. If the device is not | |
155 | "empty", i.e. it contains any signature, the operation will be skipped. It is hence expected | |
5238e957 | 156 | that this option remains set even after the device has been initialized.</para> |
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157 | |
158 | <para>Note that this option can only be used in <filename>/etc/fstab</filename>, and will be | |
159 | ignored when part of the <varname>Options=</varname> setting in a unit file.</para> | |
160 | ||
161 | <para>See | |
162 | <citerefentry><refentrytitle>systemd-mkswap@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
163 | and the discussion of | |
164 | <citerefentry project='man-pages'><refentrytitle>wipefs</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
165 | in <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
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166 | </para> |
167 | ||
168 | <xi:include href="version-info.xml" xpointer="v240"/></listitem> | |
f0c5cda2 | 169 | </varlistentry> |
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170 | </variablelist> |
171 | </refsect1> | |
172 | ||
173 | <refsect1> | |
174 | <title>Options</title> | |
175 | ||
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176 | <para>Swap unit files may include [Unit] and [Install] sections, which are described in |
177 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
178 | </para> | |
179 | ||
e9dd6984 | 180 | <para>Swap unit files must include a [Swap] section, which carries |
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181 | information about the swap device it supervises. A number of |
182 | options that may be used in this section are shared with other | |
183 | unit types. These options are documented in | |
184 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
185 | and | |
186 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
187 | The options specific to the [Swap] section of swap units are the | |
188 | following:</para> | |
189 | ||
190 | <variablelist class='unit-directives'> | |
191 | ||
192 | <varlistentry> | |
193 | <term><varname>What=</varname></term> | |
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194 | <listitem><para>Takes an absolute path of a device node or file to use for paging. See <citerefentry |
195 | project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry> for | |
196 | details. If this refers to a device node, a dependency on the respective device unit is automatically | |
197 | created. (See | |
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198 | <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
199 | for more information.) If this refers to a file, a dependency on the respective mount unit is | |
200 | automatically created. (See | |
201 | <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry> for | |
202 | more information.) This option is mandatory. Note that the usual specifier expansion is applied to | |
203 | this setting, literal percent characters should hence be written as | |
204 | <literal class='specifiers'>%%</literal>.</para></listitem> | |
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205 | </varlistentry> |
206 | ||
207 | <varlistentry> | |
208 | <term><varname>Priority=</varname></term> | |
209 | ||
210 | <listitem><para>Swap priority to use when activating the swap | |
211 | device or file. This takes an integer. This setting is | |
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212 | optional and ignored when the priority is set by <option>pri=</option> in the |
213 | <varname>Options=</varname> key.</para></listitem> | |
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214 | </varlistentry> |
215 | ||
216 | <varlistentry> | |
217 | <term><varname>Options=</varname></term> | |
218 | ||
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219 | <listitem><para>May contain an option string for the swap device. This may be used for controlling discard |
220 | options among other functionality, if the swap backing device supports the discard or trim operation. (See | |
3ba3a79d | 221 | <citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
d5cc4be2 | 222 | for more information.) Note that the usual specifier expansion is applied to this setting, literal percent |
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223 | characters should hence be written as <literal>%%</literal>.</para> |
224 | ||
225 | <xi:include href="version-info.xml" xpointer="v217"/></listitem> | |
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226 | </varlistentry> |
227 | ||
228 | <varlistentry> | |
229 | <term><varname>TimeoutSec=</varname></term> | |
230 | <listitem><para>Configures the time to wait for the swapon | |
231 | command to finish. If a command does not exit within the | |
232 | configured time, the swap will be considered failed and be | |
233 | shut down again. All commands still running will be terminated | |
234 | forcibly via <constant>SIGTERM</constant>, and after another | |
235 | delay of this time with <constant>SIGKILL</constant>. (See | |
236 | <option>KillMode=</option> in | |
237 | <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.) | |
238 | Takes a unit-less value in seconds, or a time span value such | |
239 | as "5min 20s". Pass <literal>0</literal> to disable the | |
240 | timeout logic. Defaults to | |
241 | <varname>DefaultTimeoutStartSec=</varname> from the manager | |
242 | configuration file (see | |
243 | <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>). | |
244 | </para></listitem> | |
245 | </varlistentry> | |
246 | </variablelist> | |
247 | ||
d8e1613e | 248 | <xi:include href="systemd.service.xml" xpointer="shared-unit-options" /> |
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249 | </refsect1> |
250 | ||
251 | <refsect1> | |
252 | <title>See Also</title> | |
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253 | <para><simplelist type="inline"> |
254 | <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member> | |
255 | <member><citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member> | |
256 | <member><citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member> | |
257 | <member><citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry></member> | |
258 | <member><citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry></member> | |
259 | <member><citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry></member> | |
260 | <member><citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry></member> | |
261 | <member><citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry></member> | |
262 | <member><citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry></member> | |
263 | <member><citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry></member> | |
264 | <member><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member> | |
265 | <member><citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry></member> | |
266 | </simplelist></para> | |
798d3a52 | 267 | </refsect1> |
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268 | |
269 | </refentry> |