I was having a confusing issue where after moving an ubuntu virtualbox virtual machine I was losing the virtual network adapters (i’m running one on NAT so the machine can access the internet via the host and one host-only so I can network between host and guest). After a bit of head scratching, I realised this was because the way I was “moving” a machine was by copying the hard disk image and creating a new machine. This means that the MAC addresses were getting reset. If I went into the virtualbox machine settings and changed these to the same mac addresses as were being used on the vm before it was moved, the network interfaces reappeared. I guess that’s why I should be moving the machines with the config file too..