What is the differenece between Docker Registry and Docker Index?

Question

I am new to docker and just going through the online links to understand how it works. However I am not getting much clarity on Docker Registry and Docker Index. I get that part that your docker image will be there on registry and client uses pull command to daemon which in turn get the image from registry. But I also read that you can get and image from Index as well then what is the difference between these two?

Thank you.

Answer 1

I think Where are Docker images stored? gives a good explanation:

An index manages user accounts, permissions, search, tagging, and all that nice stuff that's in the public web interface.

A registry stores and serves up the actual image assets, and it delegates authentication to the index.

When you run docker search, it's searching the index, not the registry. In fact, it might be searching multiple registries that the index is aware of.

When you run docker push or docker pull, the index determines if you are allowed to access or modify the image, but the registry is the piece that stores it or sends it down the wire to you after the index approves the operation. Also, the index figures out which registry that particular image lives in and forwards the request appropriately.

Beyond that, when you're working locally and running commands like docker images, you're interacting with something that is neither an index or a registry, but a little of both.