I run this XServe headless. I also have VirtualBox on it. To start a VM via ssh I need to first use VNC and login to the account that has permissions for VB. Then either via the Terminal application ...
This is what you should do if your VirtualBox VM boots only in the UEFI Interactive shell. We talk about Windows and Linux guest OS.
If you find yourself with a mismatched VirtualBox and VirtualBox Extension Pack release, such that VirtualBox itself cannot resolve, Jack Wallen shows you how to fix this from the command line.