Conclusions

Docker provides an alternative to virtual machines for packaging, testing, and deployment. It builds on established, albeit new in Linux, container technologies to provide process and network isolation. Additionally, by adding tools to manage images, track changes in containers, and distribute new images to others, it offers a solution that is greater than the sum of its parts. Docker's real magic is that it turns deployable images into something that can be shared and compared in a way that's quite similar to how people share and compare source code.

Docker is currently "alpha" software, and the Docker team does not claim that the product is ready for production. Features such as the ability to mount disk volumes from the host system into guest containers are still in development. A project to integrate Docker as a back-end provider for Vagrant is underway but not yet usable. The "build file" system, which enables the scripting of image creation, is effective but could be easier to use, and cleaning up after a failure to build an image is time consuming.

However, the Docker team is running a very open development process on GitHub [8]. Functionality for mounting volumes inside containers is being developed in response to feedback from users, after initially being rejected, and new feature ideas are debated in public.

In the long-term, the Docker team promises support for a wider range of kernels and for different back-end technologies, offering alternatives to LXC and Aufs. A plugin architecture is being discussed that could enable better integration with existing cloud provisioning tools. Right now, Docker is a great idea, and the current implementation offers just enough functionality to demonstrate the potential of container-based deployment. With the features already in the pipeline, Docker could be one of 2013's biggest open source projects.