SYSTEMD-BACKLIGHT@.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)