to show all vm’s
$ vboxmanage list vms
and only the running ones
$ vboxmanage list runningvms
to start one (without attaching it to the console)
$ nohup vboxheadless -s [VM-Name] &
now you can cancel with Strg-C without aborting the start of the vm
to shutdown the vm
$ vboxmanage contolvm [VM-Name] poweroff
getting some infos about the vm
$ vboxmanage showvminfo [VM-Name]
for taking a snapshot
$ vboxmanage snapshot [VM-Name] take [name of snapshot]
and to restore one
$ vboxmanage snapshot [VM-Name] restore [name of snapshot]
more details and commands @ Vbox Manual