How to find the name of intermediate Docker images?

Question

When I run docker images -a I get a lot of intermediate images. The repo and tag are <none>, but the image IDs are unique. All these images must have come from Docker hub. How can I find out the real name for these images?

Also, why do so many have the exact same virtual size?

Answer 1

These images are the intermediate layers that make up other images. Each instruction in a Dockerfile results in a new image being created. A lot of Dockerfile instructions only result in changes to the "metadata" rather than the filesystem (e.g EXPOSE, MAINTAINER) which accounts for images with the same size.

Each image may correspond to one or more "leaf" images with a repo and tag. To find these repos, you'd have to correlate the image ids with the output of running docker history on all your "leaf" images.