![]() Tip: To set the backlight depending on power state, see Power management#Using a script and an udev rule and use your favourite backlight utility in the script. etc/udev/rules.d/les ACTION="add", SUBSYSTEM="backlight", RUN+="/bin/chgrp video $sys$devpath/brightness", RUN+="/bin/chmod g+w $sys$devpath/brightness" To allow users in the video group to change the brightness, a udev rule such as the following can be used: ![]() # echo 5 > /sys/class/backlight/acpi_video0/brightnessīy default, only root can change the brightness by this method. Attempting to set a brightness greater than the maximum results in an error. The brightness can be set by writing a number to brightness. $ cat /sys/class/backlight/acpi_video0/max_brightness 15 The maximum brightness can be displayed by reading from max_brightness, which is often 15. $ ls /sys/class/backlight/acpi_video0/ actual_brightness brightness max_brightness subsystem/ uevent The directory contains the following files and subdirectories: If you use an Intel card, simply replace acpi_video0 with intel_backlight in the examples. In the following examples, acpi_video0 is used. In the case of an Intel card, the directory is called intel_backlight. In this case, the backlight is managed by an ATI graphics card. The name of the directory depends on the graphics card model. An interface to this module is provided via a sysfs(5) directory at /sys/class/backlight/. The power level can often be controlled using the ACPI kernel module for video. ![]() The brightness of the screen backlight is adjusted by setting the power level of the backlight LEDs or cathodes.
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