Docker started out as a means of creating single application containers, but since has grown into a widely used dev tool and runtime environment. It has been downloaded around two billion times, and Redmonk has said that “we have never seen a technology become ubiquitous so quickly.” The Docker registry stores container images and provides a central point of access which can be used to share containers. Users can either place images into the registry or obtain images from it to deploy directly from the registry. Despite its widespread growth and acceptance, Docker still retains its free open source roots, and hosts a free public registry for containers from which anyone can obtain official Docker images. Below is an infographic discovered via Twistlock which a really nice overview of Container technologies.
By Jonquil McDaniel