$ VBoxManage list vms
"DebC" {e35b7157-8169-449e-a75c-53acdd8449b8}
"nbsdC" {662e43a7-192f-4278-a284-34733598c278}

Start a VM in headless:

$ VBoxManage startvm nbsdC --type headless
Waiting for VM "nbsdC" to power on...
VM "nbsdC" has been successfully started.

SSH into it to see it is really running:

$ ssh deveng@ -p 2222
(deveng@ Password for deveng@nbsdc:
Last login: Sat Sep 30 10:34:05 2023 from
NetBSD 9.3 (GENERIC) #0: Thu Aug  4 15:30:37 UTC 2022

Welcome to NetBSD!

-p 2222 because port 2222 on the host i being forwarded to 22 in the VM.