How is a Docker container image retrieved from a Docker registry?

Docker retrieves a ZIP archive which is extracted into the container’s root file system.

Multiple stacked images are retrieved and layered on top of each other.

A flat hard disk image is downloaded once per container and mounted as the root file system.

The registry merger all components of the image into one file which is shipped to Docker.

The container is built from an ISO file along with a configuration for an unattended installation.