systemd.swapsystemdDeveloperLennartPoetteringlennart@poettering.netsystemd.swap5systemd.swapSwap unit configurationswap.swapDescriptionA 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.unit5
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.exec5,
which define the execution environment the
swapon8
binary is executed in, and in
systemd.kill5,
which define the way the processes are
terminated, and in
systemd.resource-control5,
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.unit5.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.<filename>fstab</filename>Swap units may either be configured via unit
files, or via /etc/fstab (see
fstab5
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-generator8
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.With 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 has the
opposite meaning and is the default.With 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
has the opposite meaning and
is the default.OptionsSwap 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.exec5
and
systemd.kill5. 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
swapon8
for details. If this refers to a
device node, a dependency on the
respective device unit is
automatically created. (See
systemd.device5
for more information.) If this refers
to a file, a dependency on the
respective mount unit is automatically
created. (See
systemd.mount5
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
swapon8
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
in
systemd.kill5.)
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.conf5).
Check
systemd.exec5
and
systemd.kill5
for more settings.See Alsosystemd1,
systemctl1,
systemd.unit5,
systemd.exec5,
systemd.kill5,
systemd.resource-control5,
systemd.device5,
systemd.mount5,
swapon8,
systemd-fstab-generator8,
systemd.directives7