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I was always unable to change my brightness since I installed Ubuntu, but I figured that installing the latest ATI driver for my graphics card would work.

I did, but I still can't change the brightness. The slider goes up and down, but the brightness stays the same (on full).

I have switchable graphics, an ATI Radeon HD 6770M, and an Intel integrated GPU.

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1 Answer

up vote 8 down vote accepted

To get working brightness key. try following

press Alt+f2 , execute gksudo gedit /etc/default/grub

Change this line

GRUB_CMLINE_LINUX_DEFAULT="quiet splash"  

to something like below

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

Open a terminal by Alt+ctrl +T, Execute sudo update-grub and reboot . See if brightness keys are working.


If the above is not working set a fixed value for brightness. To do so,

Open a terminal by pressing Alt+ctrl+T.

Type ls /sys/class/backlight/*/brightness, copy the outputs to a separate text file

The possibility is there will be two paths,try the following for each path and replace accordingly

example paths will be like

/sys/class/backlight/acpi_video0/brightness

Run following commands in terminal,

  1. For the above path Get the maximum brightness:

    cat  /sys/class/backlight/acpi_video0/max_brightness`
    

Try a lower value to set the brightness, say output is 16 so I will try with half of it

echo 8 | sudo tee  /sys/class/backlight/acpi_video0/brightness

If this works, make this happen in each login automatically by doing the following

sudo gedit /etc/rc.local

Enter this line just before exit 0. It should look like

echo YOUR_VALUE_HERE > /sys/class/backlight/acpi_video0/brightness
exit 0

Also you can try with xdotool Install xdotool

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I tried your first thing and it worked! I am just wondering if this will stay after I update? Will it stay if I uninstall the ATI Proprietary driver? I really need to know these things because I have to uninstall my ATI driver before every update or Ubuntu doesn't boot. Thank you so much! –  Yogesh Dhamija Jul 11 '12 at 15:42
    
Please reboot and see if ubuntu is remembering the brightness. Probably it won't work without driver. Because the kernel parameter tells to override brightness control from acpi driver to the graphics driver . –  Web-E Jul 11 '12 at 16:10
    
When I reboot, the brightness control still works. Thank you so much. –  Yogesh Dhamija Jul 12 '12 at 6:05
    
This is the only way I've ever had the brightness control work on my laptop (and I've tried just about everything). Now if only I could get it to remember the brightness between boots, instead it just defaults to the brightest setting. –  TomJ Aug 30 '13 at 11:24
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protected by Seth Mar 1 at 20:19

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