How can i change the screen brightness of my laptop in ubuntu?

Question

I have an acer aspire 5749 notebook with the latest version of Ubuntu(12.04 i guess), so when i change the brightness with the hot-key the brightness pane changes but actually the brightness remains the same. pleaze help me out.

Answer 1

sudo gedit /etc/default/grub

And then type your root password and insert these lines:

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

Save and exit.

sudo update-grub

Restart your laptop and then it should work by the "Fn" + left and right arrows.

Answer 2

i also have the acer aspire series laptop, and the hotkeys do not work, so you can change it by following command sudo setpci -s 00:02.0 f4.b=00, here you can enter value from 00 to ff in hexadecimal, [00 = bright and ff = dull]

for more details go through the following link : http://daksh21ubuntu.blogspot.in/2011/12/how-to-increasedecrease-brightness-on.html