CoreOS is a Linux distribution designed to run large, scalable systems. All applications deployed on a CoreOS instance are run in separate Docker containers, and CoreOS provides a suite of tools to help manage them, including etcd their own distributed configuration store. Newer services, such as fleet, help cluster management by ensuring that a specific number of service instances are always kept running. FastPatch allows atomic CoreOS upgrades using an active-passive root partition scheme and helps with quick rollback in case of problems. These new developments make CoreOS well worth looking into if you are already comfortable with Docker.