SYSTEMD-BA...T@.SERVICE(8) systemd-backlight@.serviceSYSTEMD-BA...T@.SERVICE(8)
NAME
systemd-backlight@.service, systemd-backlight - 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)
systemd 257.9 SYSTEMD-BA...T@.SERVICE(8)
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