This image is built from the Dockerfile in https://github.com/cockroachdb/k8s/tree/master/init
The image is just a tiny wrapper around the upstream, Kubernetes-maintained "peer-finder" image meant to assist with the initialization of StatefulSets.
If you run into any issues with the image, feel free to ask for help.
Thanks @rawn! I'm sorry for not seeing your comment sooner, but I've pushed an updated version.
This container is based on an old peer-finder.go, that doesn't support custom domains. See https://github.com/kubernetes/contrib/tree/master/pets/peer-finder for the latest version. This makes launching cockroachdb with this container on our k8s cluster impossible.