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systemd-backlight@.service - Man Page

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)

Referenced By

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

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

systemd 256~rc3