Comment 17 for bug 1270579

Cody, the current version of my script works only with one graphical adapter (its brightness file is named /sys/class/backlight/acpi_video0/brightness).
You can customize this value in my script at row 16
     BRIGHTNESS_CONTROL=/sys/class/backlight/acpi_video0/brightness
to path which is *correct* for your hardware.

Correct path may be determined by the following steps:
1. List all paths with brightness file in /sys/class/backlight dir with the command
     ls /sys/class/backlight/*/brightness

example:
     /sys/class/backlight/acpi_video0/brightness
     /sys/class/backlight/acpi_video1/brightness

2a. Read values of brightness from files with the command:
     cat /sys/class/backlight/*/brightness

example:
     3
     8

2b. Change backlight level with hardware keys (Fn+...) and read again:
     cat /sys/class/backlight/*/brightness

example:
     4
     8
2c. The *correct* path to brightness control file corresponds to the changed value.

example:
     /sys/class/backlight/acpi_video0/brightness # first value changed, so first file
3. Try to write brightness level manually to *correct* brightness file:
     sudo su
     echo 3 > /sys/class/backlight/acpi_video0/brightness # example on my hardware
4. Change BRIGHTNESS_CONTROL variable to the *correct* path in /etc/init.d/brightness with the command
     sudo gedit /etc/init.d/brightness

I'll update my script soon to do all steps automatically.