But I can do that with jails. I can build a master jail and distribute launch a bunch of jails from it... or distribute it to other machines... extra easy if I

But I can do that with jails. I can build a master jail and distribute launch a bunch of jails from it... or distribute it to other machines... extra easy if I use ZFS snapshots. Handle the distribution/deployment and maybe any extra configuration with your salt/ansible/whatever and you're fine. What I see as a problem here for many people is that they don't want to do this all themselves and maybe docker offers conveniences out of the box. I get that. Someone needs to work on the jails tooling to make it more approachable so people aren't inventing the wheel.