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I just installed the 64-Bit version of Ubuntu 12.04 on my newly bought Lenovo G580.

The brightness control was working properly using the Live CD and when I first started the installed version.

Then I updated Ubuntu and restarted my laptop, and suddenly now, I can't change the brightness.

I think its caused by some update. And then I went and checked my update settings, and saw that Unsupported Updates (precise-backports) were enabled by default. So now I need to fix this brightness issue somehow.

What should I do to locate the wrong update and remove it?

I don't even mind removing all the updates right now.

Thanks for the help. :)

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By unsupported updates you mean precise-backports or precise-proposed? –  LiveWireBT Sep 11 '12 at 21:41
    
precise-backports –  Arjun Bajaj Sep 12 '12 at 7:51
    
Updated the question too. –  Arjun Bajaj Sep 12 '12 at 7:52
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1 Answer

up vote 1 down vote accepted

I figured out the method to make brightness work.

I followed this thread: http://ubuntuforums.org/showthread.php?s=87102a2aa7f21edc9a672787d430af4d&t=1875126&page=2

and I added acpi_backlight=vendor to the GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" line, in /etc/default/grub

Then I ran: sudo update-grub

and I restarted my laptop, and it srtarted working. :D

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Just to complete, the full line would become: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=video" –  Gerbrand Nov 25 '13 at 8:29
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