Arch Linux VirtualBox Guest
Installing Arch under VirtualBox is straightforward, and additions should be installed through pacman (not through "Install Guest Additions" in VirtualBox, or a mounted ISO.)
Follow these instructions after doing a basic install following the Beginners' Guide.
Install the required package:
# pacman -Syu virtualbox-guest-additions
Make sure the modules are loaded:
# modprobe vboxguest # modprobe vboxsf # modprobe vboxvideo
Add the three modules above to the MODULES array in /etc/rc.conf to have them autoloaded on reboot, too.
# nano /etc/rc.conf
# vi /etc/rc.conf
If you are running something that launches /etc/xdg/autostart/vboxclient.desktop, such as GNOME, then you should be ready to go. If you use .xinitrc to launch things instead, you must:
# nano ~/.xinitrc
before launching your WM.
You should now be all set, and all guest additions should work properly. This was confirmed to work with vbox 4.0.8.
Guest additions still don't work
You may need to launch VBoxClient-all yourself. Add it to ~/.xinitrc.
Arch freezes periodically
Some people have experienced periodic, unexplained freezes. One possible reason is a VirtualBox bug related to Linux's tickless timer. Details are here http://www.ctrlaltgeek.com/category/virtualbox/
The short version is to modify /boot/grub/menu.lst and add
to the end of your kernel line.