VirtualBox
From Jon's Wiki
You're doing it wrong, use LXC instead.
List your VMs:
vboxmanage list vms vboxmanage list runningvms
Start a box from the command line.
vboxmanage startvm <vmname> --type headless
Crap, what IP is it running on? And other questions:
vboxmanage guestproperty enumerate <vmname>
Stop it:
vboxmanage controlvm <vmname> acpipowerbutton
You can use the UUID of the VM instead of the name, above.