> I think that just using containers by itself will force us to be disciplined about how we package and run services (you have to install all the stuff the serv

> I think that just using containers by itself will force us to be disciplined about how we package and run services (you have to install all the stuff the service needs inside the container, otherwise the service will not work!). > > There’s no way for it to silently depend on the host configuration, because its filesystem is totally separate from the host’s filesystem. I don't buy this, at least as presented. /etc/awesome/blah.xml does not spontaneously come into existence on a host on its own. No matter if you're building a docker image, a VM image, or managing long-lived hosts via a configuration management tool, you have to specify that /etc/awesome/blah.xml is created and has certain contents. It sounds like the author is working on a poorly structured and documented puppet codebase, where all the dependencies of services aren't clear. Presumably if they can figure them out in order to build working docker images, they could also figure them out and then refactor the Puppet code to make it more maintainable. At that point they could use their puppet code to generate their docker images, which fits nicely into the "horizontal change" philosophy.