I’ve used lemmy_migrate in the past and it’s good for one-way copy. I’ve also seen lasim, but I haven’t tried it. You may find other options on awesome-lemmy.
That’s it! If you don’t specify a host path, i.e. the path before the colon, Docker will create an volume which saves any changes you make to that path in the container, but won’t mount any existing path from the host to the container.
Are such third-party devices trustworthy? A few months ago it turned out that a lot of Android set top boxes that you can buy on Amazon come with pre-installed spyware that you can’t remove. Wouldn’t the same be a risk here?
But why would you need to disable mobile data when you enable WiFi? WiFi is automatically preferred, so having the mobile data toggle on or off doesn’t matter while connected to WiFi.
You would need to set up routes on these other devices to tell them that VPN devices can be reached through the Pi. It’s possible, but I’ve never done it myself, so I don’t have any useful pointers.