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:
sudo update-grub and reboot. Credit to this guy.
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.
/etc/default/grub, I tried just:
But it didn't work. Then I tried:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor" GRUB_CMDLINE_LINUX="acpi_osi=Linux"
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: