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I installed Ubuntu 13.10 on my Vaio nr21s but cannot adjust brightness levels. The fn keys work, but they don't change a thing, brightness remains at max level.

Thought I should choose a repository nvidia driver, but I believe it makes it worse, because the screens during boot are all messed up. So I got back to the nouveau.

Video card is nvidia 8400m gt gpu.

I know that there are plenty of threads stating the same issues, but none of the suggested solutions worked out for me.

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I faced the same problem as you are facing. But NOW it is fixed..

TO fix this follow this steps..

Open terminal(Press Ctrl + Alt +T) and Type

sudo cp /etc/default/grub /etc/default/grub.bak

press enter, and then type

sudo gedit /etc/default/grub

You will find this line in the new opened window:


Change it to:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

Save and close the window and type this in the terminal:

sudo update-grub

Restart your system..

share|improve this answer
hi, i edited the file just like you said, and brightness still not changing. i'm using the gallium driver. – user263482 Mar 30 '14 at 15:29
did you typed 'sudo update-grub' and then restarted? If yes but still not working then foollow my next answer.. – Sid Mar 31 '14 at 5:07

If above fix didn't work then repeat same steps but..

this time try to change the above mentioned line with:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash pcie_aspm=force"

then same steps and restart then reply me did it helped or not??

share|improve this answer
nothing. still no changes in brightness. – user263482 Mar 31 '14 at 17:13
no help? :((((( – user263482 Apr 2 '14 at 21:06

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