systemd-backlight@.service - Man Page

systemd-backlight@​.service

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

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

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​.

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​.

systemd(1)

kernel-command-line(7), systemd.directives(7), systemd.index(7).

The man page systemd-backlight(8) is an alias of systemd-backlight@.service(8).