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NAME | SYNOPSIS | DESCRIPTION | AUTOMATIC DEPENDENCIES | FSTAB | OPTIONS | SEE ALSO | COLOPHON |
SYSTEMD.SWAP(5) systemd.swap SYSTEMD.SWAP(5)
systemd.swap - Swap unit configuration
swap.swap
A unit configuration file whose name ends in ".swap" encodes
information about a swap device or file for memory paging controlled
and supervised by systemd.
This man page lists the configuration options specific to this unit
type. See systemd.unit(5) 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.
Additional options are listed in systemd.exec(5), which define the
execution environment the swapon(8) binary is executed in, in
systemd.kill(5), which define the way these processes are terminated,
and in systemd.resource-control(5), which configure resource control
settings for these processes of the unit.
Swap units must be named after the devices or files they control.
Example: the swap device /dev/sda5 must be configured in a unit file
dev-sda5.swap. For details about the escaping logic used to convert a
file system path to a unit name, see systemd.unit(5). Note that swap
units cannot be templated, nor is possible to add multiple names to a
swap unit by creating additional symlinks to it.
All swap units automatically get the BindsTo= and After= dependencies
on the device units or the mount units of the files they are
activated from.
Swap units with DefaultDependencies= set to its default yes value in
the "[Unit]" section enabled implicitly acquire a Conflicts= and a
Before= dependency on umount.target so that they are deactivated at
shutdown as well as a Before=swap.target dependency.
Additional implicit dependencies may be added as result of execution
and resource control parameters as documented in systemd.exec(5) and
systemd.resource-control(5).
Swap units may either be configured via unit files, or via /etc/fstab
(see fstab(5) for details). Swaps listed in /etc/fstab will be
converted into native units dynamically at boot and when the
configuration of the system manager is reloaded. See
systemd-fstab-generator(8) for details about the conversion.
If a swap device or file is configured in both /etc/fstab and a unit
file, the configuration in the latter takes precedence.
When reading /etc/fstab, a few special options are understood by
systemd which influence how dependencies are created for swap units.
noauto, auto
With noauto, the swap unit will not be added as a dependency for
swap.target. This means that it will not be activated
automatically during boot, unless it is pulled in by some other
unit. The auto option has the opposite meaning and is the
default.
nofail
With nofail, the swap unit will be only wanted, not required by
swap.target. This means that the boot will continue even if this
swap device is not activated successfully.
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 systemd.exec(5) and systemd.kill(5). The options
specific to the [Swap] section of swap units are the following:
What=
Takes an absolute path of a device node or file to use for
paging. See swapon(8) for details. If this refers to a device
node, a dependency on the respective device unit is automatically
created. (See systemd.device(5) for more information.) If this
refers to a file, a dependency on the respective mount unit is
automatically created. (See systemd.mount(5) 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 "%%".
Priority=
Swap priority to use when activating the swap device or file.
This takes an integer. This setting is optional and ignored when
the priority is set by pri= in the Options= key.
Options=
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 swapon(8) for more information.) Note that the
usual specifier expansion is applied to this setting, literal
percent characters should hence be written as "%%".
TimeoutSec=
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 SIGTERM, and after
another delay of this time with SIGKILL. (See KillMode= in
systemd.kill(5).) Takes a unit-less value in seconds, or a time
span value such as "5min 20s". Pass "0" to disable the timeout
logic. Defaults to DefaultTimeoutStartSec= from the manager
configuration file (see systemd-system.conf(5)).
Check systemd.exec(5) and systemd.kill(5) for more settings.
systemd(1), systemctl(1), systemd.unit(5), systemd.exec(5),
systemd.kill(5), systemd.resource-control(5), systemd.device(5),
systemd.mount(5), swapon(8), systemd-fstab-generator(8),
systemd.directives(7)
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2017-07-05. If you dis‐
cover any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
systemd 234 SYSTEMD.SWAP(5)
Pages that refer to this page: systemd(1), systemd.exec(5), systemd.kill(5), systemd.resource-control(5), systemd.unit(5), systemd.directives(7), systemd.index(7), systemd-fstab-generator(8), systemd-gpt-auto-generator(8)