I tend to start most of my Virtual Box guests from the command line of console with detachable (–type separate) GUI, or with no GUI at all (–type headless). Today I found the need to do some work on a running virtual machine guest through a GUI and wanted to do this from the command line without restarting the guests and realized I didn’t know how.

Powering on VirtualBox Virtual Guests

Typical guest startup methods I use from the command line:

 $ VBoxManage startvm "Trisquel8" --type separate
 $ VBoxHeadless -s "velma"

Getting to GUI from Command Line

When I start guests as above and subsequently exit the GUI, if any, and leave the guest running, I can get the GUI to display without restarting via commands like the following:

 $ VBoxManage startvm "Trisquel8" --type separate
 $ VBoxManage startvm "velma" --type separate

Conclusion

While there does not appear to be a direct command designated to allow connection to a GUI for a running guest without a GUI, issuing a start command on a running guest with a startup type that displays a GUI does display the guest in a GUI without restarting it. Unfortunately, my initial testing indicates that exiting the GUI of a running guest needs to be done from the GUI, however I may look into this further and will post an updated if I find a command line solution for exiting.