Create the following file (/etc/udev/rules.d/backlight.rules) and reboot:

>$ cat /etc/udev/rules.d/backlight.rules 

ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="intel_backlight", RUN+="/bin/chgrp video /sys/class/backlight/%k/brightness"
ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="intel_backlight", RUN+="/bin/chmod g+w /sys/class/backlight/%k/brightness"

Note, if you don’t create the file /etc/udev/rules.d/backlight.rules file then you will need to execute the commands as root.

As a member of the video group …. it will allow you to do the following:


>$ cat /sys/class/backlight/intel_backlight/actual_brightness 
3000

>$ cat /sys/class/backlight/intel_backlight/max_brightness 
7500

>$ echo 4000 > /sys/class/backlight/intel_backlight/brightness

also see the arch backlight guide

also see the arch udev guide