[ubuntu] Acer Aspire no back light

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http://ubuntuforums.org – I found an answer to this (Acer Aspire has no back light) but it is for Ubuntu version 10. Plus when I connected a monitor to the laptop, it worked fine but the laptop monitor itself won't work. I've installed Ubuntu 12.1, same situation. The laptop back light doesn't run. I have no success using the 'Fn+*< nor >*' keys to increase or decrease back light. I entered, Ctri, Alt, T in order to bring up the Terminal, which worked, then entered, gksudo gedit /etc/default/grub, which brought up grub file, then added/entered; GRUB_CMDLINELINUX_DEFAULT="quiet splash acpi_backl (Hardware)