Typing ls /sys/class/backlight/*/brightness outputs /sys/class/backlight/intel_backlight/brightness /sys/class/backlight/samsung/brightness The max_brightness for the second is 8, but changing it with echo 2 | sudo tee /sys/class/backlight/samsung/brightness doesn't change brightness. I can do it by using intel_backlight: echo 2000 | sudo tee /sys/class/backlight/intel_backlight/brightness (max_brightness: cat /sys/class/backlight/intel_backlight/max_brightness outputs 4648). But I want to do this work with the fn brightness keys, as I always did. I don't know what happened to stop working, maybe the use of +1 monitor and removing it in a wrong time or a system update. I'm using Ubuntu 12.04 64 bits in an Samsung RV420 notebook. Kernel Version is 3.2.0-27-generic. Could you help me? Please tell me what more info should I provide. Thanks!