App Container spec gains new support as a community-led effort

> I think there is much more work needed than just getting the dockerfile to reproduce a docker container. As soon as it does something like "gem install foo" or npm, pip, or yum/apt, without exactly pinning the version, you have lost.

True. However, most such tools do provide the ability to fix versions and that does work. And you now have a sensible way of building an image against an own hosted PyPI or Apt repository. You still get the benefit of having a single build and being able test in multiple places.

> The dockerfile format, while not totally horrible, still have some problems IMHO who would make it less than ideal for large scale usage.

The Dockerfile format isn't great, it has some nasty corners but it doesn't require any help from the container. The Puppet DSL is nice, but the agent is enormously heavyweight (IMHO) and has versioning issues of its own. Ansible doesn't necessarily require an agent but I find its use of YAML makes things fairly hard to read (but that might get better with practice). There's definitely some innovation required in this area.

Still, I've managed to get several people to write Dockerfiles for various things while I've never really gotten people to write much in the way of Puppet files. So they're doing something right.