Screen brightness is not changing on my ACER 5742 notebook. I have Ubuntu 10.10 installed inside Windows 7 OS. Hotkeys are used for changing brightness. Though, a bar displaying brightness level appears on screen but there is no actual change in brightness of screen.


This worked for me. Run:

gksu gedit /etc/default/grub

Change the line:


Make it say this instead:


Then run sudo update-grub and reboot. Credit to this guy.


Modifying both these lines in /etc/default/grub worked for my 4810T:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

I had the same problem with my Acer 5749. The bar displaying the brightness would show that the brightness was moving up and down, but the actual brightness wasn't changing.

In /etc/default/grub, I tried just:


But it didn't work. Then I tried:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

and that did work.

In both cases I edited the lines in /etc/default/grub then ran sudo update-grub and rebooted.

Another way, by editing just one line:

Finally I tried just:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

and that worked too. I put the other line back to how it was originally and the brightness control still works after running sudo update-grub and rebooting again:

  • I'm glad I posted this because the hard drive failed and was replaced. Now I need to fix the brightness problem again. I'll try just editing the GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub and running 'sudo update-grub'. – Chris Moore Jul 24 '12 at 23:49
  • That worked. . . – Chris Moore Jul 25 '12 at 0:58

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