I am using Apple keyboards on both my Apple and non-Apple computers, and until recently I never had problems with function keys even with Mac keyboards used on non-Apple platforms, that is, until I started to use Mac as the host for Ubuntu OS.
On "straight" Ubuntu it was always easy to enable Apple keyboards with the addition of the following line echo 2 > /sys/module/hid_apple/parameters/fnmode to the /etc/rc.local. However, in VirtualBox om Mac hosts this code does not work, because the special files and directories in /sys/module/ hierarchy do not exist, and since they are special, can not be created even by root. In particular the hid_apple/parameters/fnmode branch is missing.
None of the instructions from the Ubuntu documentation https://help.ubuntu.com/community/AppleKeyboard will fix the problem. The most interesting thing is that these files exist if Ubuntu is installed directly on the hardware, only when installed in VirtualBox on Macs there seems to be a problem. Some posts on Ubuntu forums also claim, that Ubuntu 11.10 resets the value in /sys/module/hid_apple/parameters/fnmode back to the factory setting usually a few hours after it was set during the boot time from /etc/rc.local.
The problem can be slightly mitigated by the use of <fn+F#> key combination on Apple machines, however it becomes really messy if you need to enter a more elaborate combinations like <Ctrl+Alt+fn+F1> for instance. Does anybody know, if the same mess exists on other platforms like Debian, Debian Mint, and others non-Debian based distributions?
Is there a lack of communications between Ubuntu and VirtualBox folks? Where should one report this problem with a prayer to get an answer, or perhaps a promise of a fix in future releases? On Ubuntu forum there simply isn't any interest or adequate knowledge about this issue, since it seems to happen only on VirtualBox.