Makisu by Uber is a fast and flexible Docker image building tool that works in unprivileged (e.g. userspace) containerized environments like Mesos and Kubernetes. It uses a distributed layer cache to improve performance across a build cluster. It also provides extensions (via comments) to gain greater control over generated layers with a new optional keyword (
#!COMMIT), thereby reducing the number of layers in images. Note, the Dockerfile parser in Makisu is opinionated in some scenarios. More details can be found here.