Can I Build Dockerfiles?

Currently, no.

Dockerfiles allow you to execute commands on the host system (in this case, that means Wercker), which is something we can’t allow yet. We are interested in finding a solution to this issue, but until then most of the same functionality is available by defining those commands as shell steps in your wercker.yml (and in many cases re-using steps already defined by the community).

We are working on providing some of the Docker commands as internal steps that you can leverage.

You can read a more in-depth article about our reasoning in our blog post "Dockerfiles Considered Harmful" by our CTO Andy Smith