xenial (5) systemd.swap.5.gz

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 the 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).

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= 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.

SEE ALSO

       systemd(1), systemctl(1), 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)