here's my problem:

Ever since I installed Ubuntu 12.10 on my computer I haven't been able to change the screen brightness, it was always set to the maximum. I did take a look at this post:

Decrease Backlight Below Minimum

And it helped me resolved the issue with the unbearable brightness, however one problem persists: I cannot change it through "Brightness & Lock" or the function buttons (F2 and F3), when I press the buttons, the animation shows up but nothing happens. I tried the following:


It did nothing...

If it helps:

I have an HP-dv6 6185la, it has an ATI Radeon 6770M HD card and an Intel HD Integrated Graphics Card

It only detects the "Intel® Sandybridge Mobile"

Thanks in advance.

  • I tackled this problem in such way goo.gl/VH4PN5 . There is a file /sys/class/backlight/intel_backlight/brightness to which you can write the desired value of brightness . It worked for me
    – Tebe
    Jun 1 '15 at 14:56
  • Try my fix in this article :) askubuntu.com/questions/778932/… Jun 9 '16 at 6:52
  • @Elliott-Smith : I think you should ask a new question giving specific information about your Ubuntu version. Version 12.10 is no longer supported. Sep 14 '19 at 12:58

What worked for me was to change the /etc/default/grub file as follows:

  • Open a terminal (Ctrl + Alt + T) and type sudo gedit /etc/default/grub

  • Find the line: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" and modify it to one of the following:

    GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"


    GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor" (try this if the first one doesn't work)

  • Save and close gedit.

  • Then type sudo update-grub
  • Reboot your pc.


As from Ubuntu 13.10, this did not solve the problem for me on a Toshiba laptop. I needed one extra step for the problem to be solved.

I had to create an xorg.conf file in /etc/X11/ with the following contents:

Section "Device"
       Identifier      "Configured Video Device"
       Driver          "intel"
       Option          "Backlight"       "intel_backlight"
Section "Monitor"
       Identifier      "Configured Monitor"
Section "Screen"
       Identifier      "Default Screen"
       Monitor         "Configured Monitor"
       Device          "Configured Video Device"

WARNING!! Getting the file wrong or if this configuration is not compatible with your hardware, might end up with an unbootable system! It happened to me.

In that case, you'll have to delete (or rename) the file, but to do so requires either booting from a liveUSB or liveDVD (the simplest way) or booting in recovery mode, making the Ubuntu partition rewritable and then delete the offending xorg.conf file.


Starting with kernel 4.4, the toshiba backlight device is blacklisted and doesn't appear any longer thus rendering these workarounds redundant.

  • This also works on 13.04, in case someone else is having the same issue.
    – godfrzero
    Aug 5 '13 at 18:14
  • The second one with acpi_osi=Linux worked on Debian too, thanks :>
    – Stichoza
    Dec 24 '13 at 23:51
  • It worked for me on HP Elitebook 8470p with Ubuntu 12.04 Jan 15 '14 at 9:04
  • worked on 14.04 for me, i had the second option in my grub file from 13.* already. the xorg.conf saved the day Mar 26 '14 at 3:12
  • @to-do This -> GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor" -> worked for me! Thanks a bloody lot!
    – Punit Naik
    Aug 23 '16 at 10:27

I tried several solutions, including changing grub, xbacklight, and several others. The method that works for me is changing NVIDIA settings.

  1. In terminal, gksudo gedit /etc/X11/xorg.conf
  2. Add line Option "RegistryDwords" "EnableBrightnessControl=1" immediately above EndSection
  3. Save and reboot

Here is the original page:



This solved my problem of "brightness & lock not working for changing the brightness" on Acer Aspire 5755 Ubuntu 15.04. add the following lines in the file:/usr/share/X11/xorg.conf.d/20-intel.conf

Section "Device"

  Identifier  "card0"
  Driver      "intel"
  Option      "Backlight"  "intel_backlight"
  BusID       "PCI:0:2:0"



THE REVISION for Ubuntu 17.10 , Based on this bug report. Seems little bit same issue. Follow the Developers Guide :

  1. Check the module which exactly controlling the brightness are acpi_video0 or intel_backlight.

    $ ls /sys/class/backlight/

  2. Run tee /sys/class/backlightt/acpi_video0/brightness <<< 5

    If nothing happens, then intel_backlight is the one handling the brightness settings.

  3. Next step is modifying the file /etc/default/grub include four lines.

    GRUB_CMDLINE_LINUX="acpi_backlight=none" GRUB_CMDLINE_LINUX="acpi_backlight=video" GRUB_CMDLINE_LINUX="acpi_backlight=vendor" GRUB_CMDLINE_LINUX="acpi_backlight=native"

  4. Update the grub $sudo update-grub and restart your system.

  5. The Verification.

    $ ls /sys/class/backlight/

Voila!!!! acpi_video0 is gone! Check the fn+Brightness keys or change the brightness via the applet. Brightness controls should work just fine.

Note: The Guide already on this comment #9.


Try this, it helped me with intel gpu http://ubuntufixer.blogspot.com/2012/12/set-screen-brightness-at-start-up.html

  • 5
    Welcome to Ask Ubuntu! Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. Dec 19 '12 at 1:30

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