Ask Ubuntu is a question and answer site for Ubuntu users and developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

ISSUE: Backlight brightness does not change.

More Detail: Brightness will not change, using both 'System Settings->Screen', or Fn keys (Brightness bar shows and moves, but screen brightness does not change).

Noticed a post about having multiple folders in Sys->Class->Backlight. I HAVE TWO FOLDERS TOO: intel_backlight and acpi_video0.

Using the function keys, alters the value in the acpi_video0's 'Brightness' file - But doesn't actually alter the brightness of the screen.

If I add backlight=vendor in Grub, my function keys then edit the value in the Intel_Backlight brightness file. - But again doesn't actually change the brightness of the screen.

Computer: Fujitsu Siemans Pi2515, Intel Integrated Graphics, No HDD partition.

Already Tried:

Many thanks for reading, I understand this problem may need a bit of a Linux pro to sort. If anyone up for the challenge I'll spend any amount of time being walked through this, posting results. Don't want to give up here!

share|improve this question

I have a very similar problem with a Toshiba Portege R935 in 12.04. I can't change the brightness after suspending and resuming.

The Grub line didn't help either (actually with that line, it stopped working even before suspending).

In the meantime, I discovered this workaround:

  • as root, change the value in sys/class/backlight/intel_backlight/brightness. for instance:

    echo 2937 | sudo tee /sys/class/backlight/intel_backlight/brightness

Warning: these values are not between 0 and 7 (as the ones in the other directory), but between 284 and 4539, or something like that.

share|improve this answer
One-liner that doesn't require su root? Yep, here you go: echo 2937 | sudo tee /sys/class/backlight/intel_backlight/brightness – Nathan J. Brauer Mar 18 '15 at 15:28

If you tried everything else and your system's backlight non-responsive and if you are using an Intel 915 or descendent thereof ("945GSE", etc.) then your issue may be backlight inversion confusion on gen4.

share|improve this answer
-1 The link went offline. It's essential content should have been cited here in the first place. – David Foerster Dec 31 '15 at 8:42

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

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