How to adjust screen brightness in Ubuntu 10.04

The Brightness applet in Ubuntu 10.04 seems not working: the default brightness is always set to 100, and you can't change it using the brightness applet. This is bad for both the eyes and the battery life.

You can use this command to set the brightness, instead

echo -n 70 > /proc/acpi/video/VGA/LCD/brightness

Of course, to do that, you need to be root. This can be done by "sudo bash".

Another way to do it, is to set the default brightness and other power options at System->Preference->Power Management.