systemd-backlight@.service, systemd-backlight — Load and save the display backlight brightness at boot and shutdown
systemd-backlight@.service
/usr/lib/systemd/systemd-backlight
systemd-backlight@.service is a service
that restores the display backlight brightness at early boot and
saves it at shutdown. On disk, the backlight brightness is stored
in /var/lib/systemd/backlight/. During
loading, if the udev property ID_BACKLIGHT_CLAMP is
not set to false, the brightness is clamped to a value of at
least 1 or 5% of maximum brightness, whichever is greater. This
restriction will be removed when the kernel allows user space to
reliably set a brightness value which does not turn off the
display.