I try to write a network/environment configurator for a distributed OVA appliance, similar to what Github Enterprise does, see https://github-images.s3.amazonaws.com/enterprise/Enterprise-QS-Virtualbox-Console.png. I use CoreOS and Systemd as init system. autologin is deactivated and my current approach is to write a .service unit that will setup up the network and then restart with these configurations. The reason for doing so that during systemd startup I have sufficient permissions to change network and don't have to allow the user to login. The downside is that this process basically hangs/stalls systemd startup.
My question is how to configure Systemd (in CoreOS) so that, after boot up, a user is presented with an interactive program/script and the user can't "escape" that program/script?