What’s in a Docker image?

A Docker image is a directory hierarchy containing the initial contents of a running container. It is represented by a manifest file which lists its layers, and each layer is a gzipped tarfile (.tgz files). Layers are stored as blobs named by digests of their contents.

As a sanity check, we might want to view the contents of an image that we’ve pushed to DockerHub. Following these instructions, here’s a script that fetches an image using the DockerHub Registry API. It requires jq.


Software developer in the SF Bay area. Electronic Design Automation, iOS apps, and now API tools for the world’s largest computer.