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