Closing all the Virtual running machines in the system

http://askubuntu.com/questions/457329/shutting-down-all-virtualbox-vagrant-vms-in-one-easy-to-use-bash-command-that

kondals-MacBook-Pro:~ kondalkolipaka$ VBoxManage list runningvms

"default" {f12ab661-116e-42f0-8d2b-05fc76175022}

kondals-MacBook-Pro:~ kondalkolipaka$ VBoxManage controlvm default poweroff

0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%

Here default is the VM name which is running. We can also provide UUID instead of name.