Today, I want to share a quick trick to anybody who have a problem with brightness buttons in Kubuntu Gutsy. The problem is known when you press Fn + Home (End) to adjust screen brightness in a Lenovo Thinkpad computer using Ubuntu Linux. You think that your screen will be darker or brighter but it doesn't work. There are a lot of questions about this bug on Ubuntu forum. So, if you have not yet found a proper answer may be this is a solution for you.
Open file:
vim /etc/acpi/thinkpad-brightness-up.shAdd this line before "exit"
echo 4 > /proc/acpi/ibm/cmosOpen another file:
vim /etc/acpi/thinkpad-brightness-down.shAlso insert this line before "exit"
echo 5 > /proc/acpi/ibm/cmosHopefully the problem will be fixed in your case. Read more!