Never seen it, but maybe you have DHCP or something else managing your network? It’s best to have a static network configuration (though Virtualmin installer tries to detect DHCP and configure appropriately, if this is Debian 10, you might have the new network configuration system in place, which Webmin doesn’t support yet…I don’t think that new network system is the default yet, but we have heard of people having trouble with it).
You can’t (generally) control the network from within a container. The Virtualmin installer can’t run without full control over things. I’ve tinkered with running limited Virtualmin versions within Docker, and you could make a Docker image that provides Virtualmin plus a webserver and a database for configuring and running web apps within, but it’s not really gonna be easy…and it definitely can’t be done with the Virtualmin install script.
If you’re very technical and want to tinker with it, you should start by looking at the metapackages for the dependencies (but pick and choose the ones you need…you obviously can’t be planning to run the full Virtualmin stack within a single container…that’d completely defeat the purpose of containers). Probably just web server, database, and Virtualmin+Webmin module packages, and their dependencies.
Then look at the virtualmin config-system command plugins for which ones you want to run and replicate that behavior in your container build process. For some, you may be able to just run them, as-is (e.g. virtualmin config-system --include Apache), but some are gonna choke because they depend on network or other system-level tasks that can’t be run in a container.
But, this is not a currently supported type of deployment. You’re on your own, if you go this route, so you should be confident of your skills with Linux, all the services you’ll be running, and Docker before embarking on this path.
