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On a fresh install of Ubuntu 11.04, running Unity, I can't adjust the brightness via Fn+Up/Down. The brightness panel will show, and increase/decrease accordingly, but the actual brightness never changes.

This is an issue I also had on 10.04. I used to fix this by adding this line

Option "RegistryDwords" "EnableBrightnessControl=1"

to my /etc/Xorg/xorg.conf in Section "Device". However it seems this is not working anymore. I also noticed the config file is much smaller that what I remember. Here is the whole file:

Section "Device"
Identifier      "Default Device"
    Option  "NoLogo"        "True"
    Option  "RegistryDwords"        "EnableBrightnessControl=1" 
EndSection

Should I use this line somewhere else ? or is there something else to fix ?

For reference, here is the original issue on 10.04: https://answers.launchpad.net/ubuntu/+source/xserver-xorg-video-nv/+question/109012

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Did you solve the problem? I've got the same on my 3500... –  Mateusz May 14 '11 at 16:08
    
No, not solved. I'll post the answer if I find it. –  PowerKiKi May 15 '11 at 11:06

2 Answers 2

up vote 3 down vote accepted

i have same problem on dell vostro 3500 and solution from this question helped me to fix brightness bug: Screen brightness not changing on Acer 5742 notebook.

The complete solution is:

  1. edit /etc/Xorg/xorg.conf to add the following line in Section "Device":

    Option "RegistryDwords" "EnableBrightnessControl=1"
    
  2. edit /etc/default/grub to change the line into:

    GRUB_CMDLINE_LINUX="acpi_osi=Linux"
    
  3. run the command:

    sudo update-grub
    
  4. reboot

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It worked for me, however I had to re-add the line in my xorg.conf as described in the OP. Thank to everybody involved in this answer ;-) –  PowerKiKi May 18 '11 at 21:39
    
It's still working for Ubuntu 11.10 –  PowerKiKi Nov 15 '11 at 1:06
    
It also works for Ubuntu 12.04 (Dell Inspiron 17R 7720; used "acpi_osi=" instead though but still worked) –  NPatel Dec 27 '12 at 4:12
    
Still working on 13.04 with one difference. There is no xorg.conf by default. To create one stop Xorg and run from root following commands: X -configure and then cp /root/xorg.conf.new /etc/X11/xorg.conf –  Novarg Jun 16 '13 at 13:03

I believe you need to install Nvidia blacklight driver (nvidia-bl-dkms). The package itself has been developed for MacBooks, but they use same Nvidia model – G310M.

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Sounds like a good idea, but unfortunately it didn't help at all, even after a reboot. Another guy has similar result: ubuntuforums.org/showthread.php?p=10817972 –  PowerKiKi May 15 '11 at 11:05

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