Container technology remains very big news, and if you bring up the topic almost everyone immediately thinks of Docker. But, there are other tools that can compete with Docker, and tools that can extend it and make it more flexible. CoreOS’s Rkt, for example, is a command-line tool for running app containers. And, ClusterHQ has an open source project called Flocker that allows developers to run their databases inside Docker containers, leveraging persistent storage, and making data highly portable.