man > systemd.swap(5)

SYSTEMD.SWAP(5)                             systemd.swap                             SYSTEMD.SWAP(5)

NAME
       systemd.swap - Swap unit configuration

SYNOPSIS
       swap.swap

DESCRIPTION
       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) program 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.

       Note that swap support on Linux is privileged, swap units are hence only available in the
       system service manager (and root's user service manager), but not in unprivileged user's
       service manager.

AUTOMATIC DEPENDENCIES
   Implicit Dependencies
       The following dependencies are implicitly added:

       •   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.

       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).

   Default Dependencies
       The following dependencies are added unless DefaultDependencies=no is set:

       •   Swap units automatically 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.

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. The auto option has the opposite meaning and is the default.

           Added in version 218.

       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.

           Added in version 218.

       x-systemd.device-timeout=
           Configure how long systemd should wait for a device to show up before giving up on an
           entry from /etc/fstab. Specify a time in seconds or explicitly append a unit such as "s",
           "min", "h", "ms".

           Note that this option can only be used in /etc/fstab, and will be ignored when part of
           the Options= setting in a unit file.

           Added in version 215.

       x-systemd.makefs
           The swap structure will be initialized on the device. If the device is not "empty", i.e.
           it contains any signature, the operation will be skipped. It is hence expected that this
           option remains set even after the device has been initialized.

           Note that this option can only be used in /etc/fstab, and will be ignored when part of
           the Options= setting in a unit file.

           See systemd-mkswap@.service(8) and the discussion of wipefs(8) in systemd.mount(5).

           Added in version 240.

OPTIONS
       Swap unit files may include [Unit] and [Install] sections, which are described in
       systemd.unit(5).

       Swap unit 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 "%%".

           Added in version 217.

       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.unit(5), systemd.exec(5), and systemd.kill(5) for more settings.

SEE ALSO
       systemd(1), systemctl(1), systemd-system.conf(5), 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)

systemd 255                                                                          SYSTEMD.SWAP(5)