Unable to change brightness on a toshiba m505

Question

I got Toshiba m505 and I can't change the brightness of my screen. I can see the brightness adjusting bar move when I use fn+F6 or fn+F7 keys but nothing happens. I'm using Ubuntu 12.04. I did a lot of search on-line but I can't find anything clear for me to understand.

Answer 1

Sometimes the kernel needs a parameter. Try this:

Open a terminal (Ctrl+Alt+T) and give this command

gksudo gedit /etc/default/grub

at the opened window , search for this line GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

and change it to look exactly like this

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi="

proofread , save the document and then

run in terminal this command

sudo update-grub

Reboot your PC and see if problem solved.