systemd-backlight@.service, systemd-backlight - Load and save the display
backlight brightness at boot and shutdown
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.
systemd-backlight understands the following kernel command line parameter:
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.