I still don't "get" docker. I've deployed systems with it, and it works fine (maybe except for postgres containment, there still seems to be some "bare metal as

I still don't "get" docker. I've deployed systems with it, and it works fine (maybe except for postgres containment, there still seems to be some "bare metal assumptions" that postgres may use that docker may invalidate), but why not use Ansible/Vagrant to build images? It appears (to me) to be the same thing, but with new mental overhead and/or cult involved. Lots of ways to make sure that images get built and tested and deployed by scripts that keep a lot of config and directory in stand-alone (twinned) services. Why there is a "docker" cult (which may be the wrong word - it may be very very valid) escapes me.