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
    Commented 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
    Commented Feb 24, 2011 at 13:12
  • What distro do you use?
    – tshepang
    Commented Feb 24, 2011 at 13:18
  • I use Ubuntu, but with a kernel on my own (2.6.37).
    – profy
    Commented 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
    Commented Feb 24, 2011 at 13:15
  • I've tried this, and I'm, still sitting with the problem.
    – tshepang
    Commented Feb 24, 2011 at 15:34
  • It's a /boot/grub/menu.lst
    – 1vanu4
    Commented Feb 27, 2011 at 22:48
  • In my situation it helped me.
    – 1vanu4
    Commented Feb 27, 2011 at 22:49
  • SO you can now adjust brightness using special laptop shortcuts, as in my case?
    – tshepang
    Commented 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
    Commented Mar 18, 2020 at 1:07

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