I cannot change the screen brightness

by Cube   Last Updated September 11, 2019 22:02 PM

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.

Answers 5

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.

To Do
To Do
December 14, 2012 00:01 AM

I was do the same as above.

It was do nothing.

Then I had to leave my g75VW and closed the lid.

I come back after a while then I opened the lid and then the backlight was working with F5/F6 as it should be…

Only the onscreen display not showing…

I tried again with lid closing and after a while open it and it still working..

Hope it's helps.

December 17, 2012 15:18 PM

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

December 17, 2012 17:31 PM

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:


August 15, 2013 23:23 PM

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"


Rahul Shaw
Rahul Shaw
September 15, 2015 07:05 AM

Related Questions

Ubuntu 18.04 LTS Backlight function key

Updated May 17, 2019 14:02 PM

Security risk with scripts that write to /sys/class

Updated September 24, 2018 00:02 AM

How to increase brightness in smaller steps?

Updated February 28, 2017 12:02 PM

Decrease Backlight Below Minimum

Updated April 27, 2017 06:02 AM