Done when:

Get sign off from CoreOS team.

Future considerations:

While the Dockerfile that BuildController generates works as it should, there are a few outstanding questions about it. For example:

• Are we calling Ignition correctly?
• Can we auto-detect / mutate Dockerfiles provided by cluster admins? Can we preemptively return an error if the Dockerfile they provide is invalid? Perhaps by parsing using a Dockerfile AST (abstract syntax tree), e.g., https://github.com/openshift/imagebuilder/tree/master/dockerfile/parser?
• Should the custom Dockerfile be executed first before the MachineConfigs and the remainder are applied?