Create a clone of an existing virtual machine (VM). More information: https://www.virtualbox.org/manual/ch08.html#vboxmanage-clonevm.
VBoxManage clonevm vm_name
VBoxManage clonevm vm_name --name new_vm_name
VBoxManage clonevm vm_name --basefolder path/to/directory
VBoxManage clonevm vm_name --register