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I've installed Ubuntu 12.04 on my Toshiba Satellite L645D and the screen brightness does not work. Any suggestions?

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This worked for me. – To Do Nov 7 '12 at 15:28

You might want to edit your xorg.conf configuration. In a terminal, type:

sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.backup

This will make a backup of your xorg.conf file - just in case :) That being done, type:

gksudo gedit /etc/X11/xorg.conf

and under Section "Device" add the following line:

Option "RegistryDwords" "EnableBrightnessControl=1"

Save and reboot.

Perhaps this already does the trick. In that case, congratulations!

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I know it is a bit late but I had the exact same problem with my girlfriend's computer, a Toshiba Satellite L645D with Ubuntu 14.04 LTS. I think this fix should also work on this computer model with other Debian-related Distros.

After searching and trying everything in the web I found this page:

Keybinding to change brightness by way of acpi brightness file?

So what I did to fix the problem was open /etc/default/grub with nano (or whatever text editor you may like):

sudo nano /etc/default/grub

And search the line that starts with: GRUB_CMDLINE_LINUX_DEFAULT="(something)" I don't remember exactly what text it had on the quotes. And make it look like:

GRUB_CMDLINE_LINUX_DEFAULT="acpi_osi=Linux acpi_backlight=vendor"

Then update the grub with:

sudo update-grub

Finally, reboot and that's it! Hope that helps :D

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