How to Solve Brightness-is-not-changing Issue in 12.04

Actually, the issue I’m talking about is the fact of not being able to change the screen brightness (backlight), neither using Fn key nor using “Brightness and Lock” in system settings. The solution is to change the brightness value in a specific file, manually.

To do that, you only need to run the following command, and the brightness will change instantly. Don’t forget to enter your root password whenever you’re asked to.

If you’ve got an Intel itegrated GPU :

sudo -s

echo 60 > /sys/class/backlight/intel_backlight/brightness

I had an ATI Radeon video card, and this used to work, but here, the highest value is 7 instead of 100:

sudo -s

echo 5 > /sys/class/backlight/acpi_video0/brightness

  • shah

    bash: /sys/class/backlight/acpi_video0/brightness: No such file or directory

  • Suresh meeraj

    my brightness haven’t changed by doing so

    • http://followthegeeks.com Mohamed Semlali

      I’m sorry for this. please try echo 60 > /sys/class/backlight/intel_backlight/brightness if you have an integrated intel GPU.

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  • Carlton

    it worked to dim my laptop, but now it won’t go brighter again.
    Dell Inspiron n7010

    • Carlton

      nevermind, I figured it out. I navigated to /sys/class/backlight/intel_backlight in the file manager and saw that the “max_brightness” was set to 4882, not 100

      • http://curricontracting.com Curconinc

        I have an Inspiron 5520 doing the same thing. I do not know, however, what you mean or how to navigate “to /sys/class/backlight/intel_backlight in the file manager” to change my “max_brightness” as you did. Help much appreciated!

        • Carlton

          alright so open the file manager (just go to your home folder or something).

          1. click on “filesystem” on the left hand side.
          2. “sys” folder
          3. “class” folder
          4. “backlight” folder
          5. “intel_backlight” folder

          in here you’ll see the files controlling your computer’s brightness. the
          “brightness” and “actual_brightness” files show the current brightness level. the one you’re concerned with is “max_brightness”. I didn’t actually change that file. when I do the brightness command in the article, I just set the value to between 500 and 3000, since any
          brighter than that my laptop turns into a flashlight and hurts to look at.

          • http://curricontracting.com Curconinc

            Thank you for your reply. My “brightness” and “actual_brightness” are set at 2000. Nice and bright. My “max_brightness” is set at 4882. Still can’t adjust brightness with my keys or slider. Not sure what to do. Are you saying the only way to adjust brightness is through the command in the article, changing the value as needed? Thank you.

          • Carlton

            the command in the article is the only one I’ve managed to get it to work, and I did it that way for like 6 months. what I ended up doing eventually was writing a short program in C that would take the value of the brightness file and increment in by like 400 up or down. Then I mapped it to a key combination so I can change it using the buttons.

  • Abdul

    I’m having 105m nvidia graphics card, i’m having this problem in ubuntu 12.04,12.10,13.04 and linux mint also. I don’t have intel_backlight folder but acpi_video0. After running the cmd, use any value, nothing is happening. Actually value is changing but not the brightness. I tried by edit xorg.conf, grub everything. no use. If you have any other solution, please suggest it.

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  • quantenfrik

    worked perfectly, you’re awesome thx!