I was confused as to make slugrunner start a container in detached mode (-d and -a flags conflict). The following seems to work: cat /tmp/slug.tar.gz | docker run -i -a stdin flynn/slugrunner start web

The stackbrew/hipache docker image uses Redis 2.2, which means you need to be careful because rpush only supports a single argument. I attempted to add multiple arguments using the Python client, the data ended up garbled, and hipache basically does no logging whatsoever, so this is a paint to figure out.