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)

systemd 257.4                                                                      SYSTEMD-BACKLIGHT@.SERVICE(8)