Storing and sharing container images

So far, you have already pulled your first hello-world container with the docker pull hello-world command and even used the docker run hello-world command. Under the hood, a few things happen during an image pull:

1. Docker Engine connects to the so-called Docker image registry. The registry can be specified explicitly, but by default, this is the official public registry, called Docker Hub (https://hub.docker.com/).
2. Docker Engine authenticates to the registry, if needed. This can be the case if you are running a private registry or paid plan for Docker Hub.
3. The selected hello-world image is downloaded as a set of layers identified by SHA256 digests. Each layer is unpacked after being downloaded.
4. The image is stored locally.

A similar procedure happens if you execute the docker run command and the image is not present in the local store. The...