Shipping applications is an integral part of the Docker platform. The Docker Engine can download images from a central location to run containers from them, and can also upload images which were built locally to a central location. These shared image stores are called registries, and in this chapter we'll look more closely at how image registries work and the types of registries that are available to you.
The primary image registry is Docker Hub, which is a free online service and is the default location for the Docker service to work with images. Docker Hub is a great place for the community to share images which are built to package open source software and are free to redistribute. Docker Hub has been hugely successful. At the time of writing this book, there are hundreds of thousands of images available on it, with billions of downloads...