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)