VBoxManage is the command line way to manage your VirtualBox hosts.
VBoxManage showvminfo
VBoxManage list vms
VBoxManage list runningvms
VBoxManage startvm $vm --type=headless
VBoxManage startvm $vm --type=gui
VBoxManage controlvm $vm savestate
VBoxManage controlvm $vm poweroff
VBoxManage modifyvm $vm --accelerate3d=off
VBoxManage modifyvm backend --memory 256
Mount Shared folder
mount -t vboxsf -o uid=1000,gid=1000 Shared Shared/
Shrink Virtualbox VM
If your virtual disk looks full but not really as much, the you can shrink Virtualbox VM disk with the following:
sudo apt-get zerofree
reboot and start in Init 1 mode
mount -n -o remount,ro -t ext3 /dev/sda1 /
zerofree /dev/sda1
shutdown -h now
Once done, go back to the master host and
VboxManage modifyvdi /path/to/your/VM.vdi compact
Clone VirtualMachine
VBoxManage clonevm --name newvm --register --basefolder VirtualBox\ VMs/oldvm