systemd-backlight@.service(8) — Linux manual page

SYSTEMD-....SERVICE(8) systemd-backlight@.service SYSTEMD-....SERVICE(8)

NAME

       systemd-backlight@.service, systemd-backlight - Load and save the
       display backlight brightness at boot and shutdown

SYNOPSIS

       systemd-backlight@.service

       /usr/lib/systemd/systemd-backlight save [backlight|leds]:DEVICE

       /usr/lib/systemd/systemd-backlight load [backlight|leds]:DEVICE

DESCRIPTION

       systemd-backlight@.service is a service that restores the
       brightness of a display backlight or LED (e.g. keyboard
       backlight) device at early boot, and saves it at shutdown. The
       brightness is stored in /var/lib/systemd/backlight/.

       On restoring brightness of a display backlight device,
       systemd-backlight reads ID_BACKLIGHT_CLAMP udev property, that
       takes a boolean value or a percentage (needs to be suffixed with
       "%", e.g.  "30%"). When a percentage is specified, the saved
       brightness is clamped to a value of at least 1 or the specified
       percentage of the maximum brightness, whichever is greater. When
       unset or set to true, the brightness is clamped in the same way
       with percentage 5%. When false, the saved brightness will not be
       clamped, and loaded as is.

       On restoring brightness of a LED device, systemd-backlight reads
       ID_LEDS_CLAMP udev property, that also takes a boolean value or a
       percentage. When a percentage is specified, the saved brightness
       is clamped to the specified percentage of the maximum brightness.
       When set to true, the brightness is clamped in the same way with
       percentage 5%. When unset or set to false, the saved brightness
       will not be clamped, and loaded as is.

KERNEL COMMAND LINE

       systemd-backlight understands the following kernel command line
       parameter:

       systemd.restore_state=
           Takes a boolean argument. Defaults to "1". If "0", does not
           restore the backlight settings on boot. However, settings
           will still be stored on shutdown.

           Added in version 209.

SEE ALSO

       systemd(1)

COLOPHON

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have
       a bug report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
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systemd 257~devel                                 SYSTEMD-....SERVICE(8)

Pages that refer to this page: kernel-command-line(7), systemd.directives(7), systemd.index(7)

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