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.
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.
Unless the noauto option is set
                for them all swap units configured in
                /etc/fstab are also added as
                requirements to swap.target, so
                that they are waited for and activated during
                boot.
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.
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
                                90s.
Check systemd.exec(5) and systemd.kill(5) for more settings.