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'\" t
.TH "SYSTEMD\-BACKLIGHT@\&.SERVICE" "8" "" "systemd 256~rc3" "systemd-backlight@.service"
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.SH "NAME"
systemd-backlight@.service, systemd-backlight \- Load and save the display backlight brightness at boot and shutdown
.SH "SYNOPSIS"
.PP
systemd\-backlight@\&.service
.PP
/usr/lib/systemd/systemd\-backlight
save [backlight|leds]:DEVICE
.PP
/usr/lib/systemd/systemd\-backlight
load [backlight|leds]:DEVICE
.SH "DESCRIPTION"
.PP
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/\&.
.PP
On restoring brightness of a display backlight device,
\fBsystemd\-backlight\fR
reads
\fIID_BACKLIGHT_CLAMP\fR
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\&.
.PP
On restoring brightness of a LED device,
\fBsystemd\-backlight\fR
reads
\fIID_LEDS_CLAMP\fR
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\&.
.SH "KERNEL COMMAND LINE"
.PP
systemd\-backlight
understands the following kernel command line parameter:
.PP
\fIsystemd\&.restore_state=\fR
.RS 4
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\&.
.sp
Added in version 209\&.
.RE
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1)
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