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, and in systemd.kill(5), which define the way the processes are terminated, and in systemd.resource-control(5), which configure resource control settings for the processes of the service.
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).
All swap units automatically get the appropriate dependencies on the devices or on the mount points of the files they are activated from.
Swap units with
DefaultDependencies= enabled
implicitly acquire a conflicting dependency to
umount.target so that they are
deactivated at shutdown.
fstab¶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. Option auto has the
opposite meaning and is the default.
nofail, fail¶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. Option
fail has the opposite meaning and
is the default.
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.
Priority=¶Swap priority to use when activating the swap device or file. This takes an integer. This setting is optional.
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.)
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.