VBoxManage
VBoxManage is used to control VirtualBox instances from the command-line. You can, fex, start an instance headless.
Get the list of options:
VBoxManage controlvm
Start, stop, reset, etc.:
VboxManage controvm <vmname> pause VboxManage controvm <vmname> resume VboxManage controvm <vmname> reset VboxManage controvm <vmname> poweroff VboxManage controvm <vmname> savestate VboxManage controvm <vmname> acpipowerbutton
