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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | KERNEL COMMAND LINE | SEE ALSO | COLOPHON |
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SYSTEMD-....SERVICE(8) [email protected] SYSTEMD-....SERVICE(8)
[email protected], systemd-backlight - Load and save the
display backlight brightness at boot and shutdown
[email protected]
/usr/lib/systemd/systemd-backlight save [backlight|leds]:DEVICE
/usr/lib/systemd/systemd-backlight load [backlight|leds]:DEVICE
[email protected] 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.
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.
systemd(1)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 258~rc2 SYSTEMD-....SERVICE(8)
Pages that refer to this page: kernel-command-line(7), systemd.directives(7), systemd.index(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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