I ran into an obscure problem with VirtualBox. For weeks I had been using a virtual machine (VM) for some specific testing. I always launched the VM from the VirtualBox GUI.
As part of my testing I attempted to launch the VM headless from the command line and received the following message:
VBoxManage: error: Could not find a registered machine named....
I returned to the GUI and the VM launched.
Everything I read online about registering a machine did not help. Looking for a proverbial needle in the haystack I began comparing configuration files of all VMs.
I discovered the hard disk of the problematic VM was listed in another machine’s configuration as a second disk. Sometimes I temporarily move disks from one VM to another as a quick way to copy or sync files without configuring any network. Somehow after I completed such a task the disk was not removed from the second VM’s configuration. Possibly user error although I have done this many times.
To add to the mystery, the GUI did not list the disk in the second machine’s
Storage configuration. More weird is the GUI showed the disk in the correct VM
Storage, but the disk was not itemized in the respective configuration file.
Manually deleting the hard disk from the second machine’s configuration and manually adding the hard disk to the correct machine configuration resolved the problem.