Hi @drcnyc,
Could you help me remember the config.json update process?
The essence of the cutover process is just updating config.json to point to the new API server. There is a service that watches config.json and will apply the change, reconfigure the VPN and restart the supervisor.
If I’m not mistaken, the only way to update the config.json (without using balena join from the CLI) is by SSHing into the device and running a command I can’t recall 
which was something like update_command "config.json content on a single line". For the config.json, I’d use the one I injected into the image before flashing the device (which adds keys after provisioning), but I have a doubt about an apiKey that’s present in this file but not in the provisioned one, for which I can’t find any documentation.
Is the mirror of the old registry database to avoid having to redeploy the application?
You’ll also want to make sure the new balena environment had a mirror of the old database, registry etc. Otherwise you will have to manually register the device. If you prefer to start clean, you can automate that in a shell script as well, but you’ll want to make sure that if you get a new UUID or API key that you apply those to config.json in addition to the API server.
I’m also interested in this scenario as I’m currently dealing with this problem: Build on Internet-Connected Machine and Deploying to Internet-Isolated Environment (in which I believe I’ve made some progress), but the device I tried to move with the wizard using the balena join CLI isn’t downloading the application. And it seems to me that it’s not properly moved even if it says “operational”, so I wanted to try moving it by injecting the config.json from the device.
Thanks