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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) 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.

AUTOMATIC DEPENDENCIES

   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= in the "[Unit]" section enabled
   implicitly acquire a Conflicts= and an After= dependency on
   umount.target so that they are deactivated at shutdown, unless
   DefaultDependencies=no is specified.

   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).

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.

   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.

OPTIONS

   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 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.)

   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.

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