Screen brightness not changing on Acer 5742 notebook

Question

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.

Answer 1

this worked for me. Many Thanks!

sudo gedit /etc/default/grub

Change the line :

GRUB_CMDLINE_LINUX=""

to

GRUB_CMDLINE_LINUX="acpi_osi=Linux"

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

Answer 2

modify both lines worked for my 4810T:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor" GRUB_CMDLINE_LINUX="acpi_osi=Linux"