1SYSTEMD.SWAP(5) systemd.swap SYSTEMD.SWAP(5)
2
6 systemd.swap - Swap unit configuration
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9 swap.swap
10
12 A unit configuration file whose name ends in ".swap" encodes
13 information about a swap device or file for memory paging controlled
14 and supervised by systemd.
15 This man page lists the configuration options specific to this unit
17 type. See systemd.unit(5) for the common options of all unit
18 configuration files. The common configuration items are configured in
19 the generic [Unit] and [Install] sections. The swap specific
20 configuration options are configured in the [Swap] section.
21 Additional options are listed in systemd.exec(5), which define the
23 execution environment the swapon(8) program is executed in, in
24 systemd.kill(5), which define the way these processes are terminated,
25 and in systemd.resource-control(5), which configure resource control
26 settings for these processes of the unit.
27 Swap units must be named after the devices or files they control.
29 Example: the swap device /dev/sda5 must be configured in a unit file
30 dev-sda5.swap. For details about the escaping logic used to convert a
31 file system path to a unit name, see systemd.unit(5). Note that swap
32 units cannot be templated, nor is possible to add multiple names to a
33 swap unit by creating additional symlinks to it.
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36 Implicit Dependencies
37 The following dependencies are implicitly added:
38 · All swap units automatically get the BindsTo= and After=
40 dependencies on the device units or the mount units of the files
41 they are activated from.
42 Additional implicit dependencies may be added as result of execution
44 and resource control parameters as documented in systemd.exec(5) and
45 systemd.resource-control(5).
46 Default Dependencies
48 The following dependencies are added unless DefaultDependencies=no is
49 set:
50 · Swap units automatically acquire a Conflicts= and a Before=
52 dependency on umount.target so that they are deactivated at
53 shutdown as well as a Before=swap.target dependency.
54
56 Swap units may either be configured via unit files, or via /etc/fstab
57 (see fstab(5) for details). Swaps listed in /etc/fstab will be
58 converted into native units dynamically at boot and when the
59 configuration of the system manager is reloaded. See systemd-fstab-
60 generator(8) for details about the conversion.
61 If a swap device or file is configured in both /etc/fstab and a unit
63 file, the configuration in the latter takes precedence.
64 When reading /etc/fstab, a few special options are understood by
66 systemd which influence how dependencies are created for swap units.
67 noauto, auto
69 With noauto, the swap unit will not be added as a dependency for
70 swap.target. This means that it will not be activated automatically
71 during boot, unless it is pulled in by some other unit. The auto
72 option has the opposite meaning and is the default.
73 nofail
75 With nofail, the swap unit will be only wanted, not required by
76 swap.target. This means that the boot will continue even if this
77 swap device is not activated successfully.
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80 Swap files must include a [Swap] section, which carries information
81 about the swap device it supervises. A number of options that may be
82 used in this section are shared with other unit types. These options
83 are documented in systemd.exec(5) and systemd.kill(5). The options
84 specific to the [Swap] section of swap units are the following:
85 What=
87 Takes an absolute path of a device node or file to use for paging.
88 See swapon(8) for details. If this refers to a device node, a
89 dependency on the respective device unit is automatically created.
90 (See systemd.device(5) for more information.) If this refers to a
91 file, a dependency on the respective mount unit is automatically
92 created. (See systemd.mount(5) for more information.) This option
93 is mandatory. Note that the usual specifier expansion is applied to
94 this setting, literal percent characters should hence be written as
95 "%%".
96 Priority=
98 Swap priority to use when activating the swap device or file. This
99 takes an integer. This setting is optional and ignored when the
100 priority is set by pri= in the Options= key.
101 Options=
103 May contain an option string for the swap device. This may be used
104 for controlling discard options among other functionality, if the
105 swap backing device supports the discard or trim operation. (See
106 swapon(8) for more information.) Note that the usual specifier
107 expansion is applied to this setting, literal percent characters
108 should hence be written as "%%".
109 TimeoutSec=
111 Configures the time to wait for the swapon command to finish. If a
112 command does not exit within the configured time, the swap will be
113 considered failed and be shut down again. All commands still
114 running will be terminated forcibly via SIGTERM, and after another
115 delay of this time with SIGKILL. (See KillMode= in
116 systemd.kill(5).) Takes a unit-less value in seconds, or a time
117 span value such as "5min 20s". Pass "0" to disable the timeout
118 logic. Defaults to DefaultTimeoutStartSec= from the manager
119 configuration file (see systemd-system.conf(5)).
120 Check systemd.exec(5) and systemd.kill(5) for more settings.
122
124 systemd(1), systemctl(1), systemd.unit(5), systemd.exec(5),
125 systemd.kill(5), systemd.resource-control(5), systemd.device(5),
126 systemd.mount(5), swapon(8), systemd-fstab-generator(8),
127 systemd.directives(7)
128systemd 239 SYSTEMD.SWAP(5)