My laptop has keyboard buttons for adjusting screen brightness. After a Debian Squeeze re-installation, they don't work no more.

[laptop] Acer TravelMate 6592; I use Fn< to decrease the brightness and Fn> to increase it.

  • These things can sometimes be brand/model specific so a bit of information about the laptop in question might be useful.
    – Steven D
    Feb 10, 2011 at 17:42

4 Answers 4


Is it a problem of key mapping or a problem of acpi support ?

Check in /proc/acpi/ if you have some entries like this one : /proc/acpi/video/GFX0/LCDD/brightness

If you find it, try to set a value maybe like this :

echo "4" > /proc/acpi/video/GFX0/LCDD/brightness
  • I don't have the "/prc/acpi/video" directory. My kernel is 2.6.32 on Debian.
    – tshepang
    Feb 24, 2011 at 13:12
  • What distro do you use?
    – tshepang
    Feb 24, 2011 at 13:18
  • I use Ubuntu, but with a kernel on my own (2.6.37).
    – profy
    Feb 25, 2011 at 20:23

Add "acpi_osi=Linux" to loader


title Arch Linux
root (hd0,1)
kernel /vmlinuz26 root=/dev/sda5 ro acpi_osi=Linux
initrd /kernel26.img
  • What is loader?
    – tshepang
    Feb 24, 2011 at 13:15
  • I've tried this, and I'm, still sitting with the problem.
    – tshepang
    Feb 24, 2011 at 15:34
  • It's a /boot/grub/menu.lst
    – 1vanu4
    Feb 27, 2011 at 22:48
  • In my situation it helped me.
    – 1vanu4
    Feb 27, 2011 at 22:49
  • SO you can now adjust brightness using special laptop shortcuts, as in my case?
    – tshepang
    Mar 25, 2011 at 20:59

It's probably the case that it got removed in the latest Debian Squeeze kernel (which is where the problem was), and it's now put back in 2.6.38. I say that because it was working way before Squeeze was released (and I only use pristine Debian kernel packages).


If you can change your brightness with root user by typing:

echo 100 > /sys/class/backlight/<xxx>/brightnes

Then, you can follow this link: https://askubuntu.com/a/82320/301773

  • For example /sys/class/backlight/intel_backlight/brightness for thinkpads
    – holms
    Mar 18, 2020 at 1:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.