systemd.swap(5) — Linux manual page


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

NAME         top

       systemd.swap - Swap unit configuration

SYNOPSIS         top


DESCRIPTION         top

       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.


   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

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

       ·   Swap units automatically acquire a Conflicts= and a Before=
           dependency on so that they are deactivated at
           shutdown as well as a dependency.

FSTAB         top

       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
  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

           With nofail, the swap unit will be only wanted, not required by
  This means that the boot will continue even if this
           swap device is not activated successfully.

           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",

           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.

           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

OPTIONS         top

       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

           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 "%%".

           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.

           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 "%%".

           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         top

       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)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug
       report for this manual page, see
       ⟨⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨⟩ on 2020-09-18.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-09-18.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to

systemd 246                                                  SYSTEMD.SWAP(5)

Pages that refer to this page: init(1)systemd(1)systemd.exec(5)systemd.kill(5)systemd.resource-control(5)systemd.unit(5)30-systemd-environment-d-generator(7)systemd.directives(7)systemd.index(7)systemd.syntax(7)systemd-fstab-generator(8)systemd-gpt-auto-generator(8)