On Linux, for some reason Apple keyboards' function keys don't work by default. Most of them try to run special functions instead, like volume up/down or play/pause.
But you can get normal function keys by talking to the kernel module that drives the keyboard:
echo 2 > /sys/module/hid_apple/parameters/fnmode
This will only last until shutdown, so put that line in /etc/rc.local or a similar place so it runs every time you boot.
Here's an Ubuntu help page on Apple Keyboards with more information and other tricks.
[ 16:03 Apr 15, 2010 More linux/kernel | permalink to this entry | comments ]