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. Run:

gksu gedit /etc/default/grub

Change the line:

GRUB_CMDLINE_LINUX=""

Make it say this instead:

GRUB_CMDLINE_LINUX="acpi_osi=Linux"

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

Answer 2

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

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

Answer 3

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:

GRUB_CMDLINE_LINUX="acpi_osi=Linux"

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:

GRUB_CMDLINE_LINUX=""