I would like to ask why it is needed to specify both name and digest when pulling docker image?
docker pull ubuntu@sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2
Isn't it enough, just to pass the digest, or the digest is not unique enough in the context of the whole docker repository?
For example like that:
docker pull sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2
Images are pulled from registries. Image names include the registry, e.g. quay.io/yourgroup/yourimage pulls from quay.io server.
But ubuntu doesn't include the server name, you say?
If there's no server name, it defaults to the Docker Hub, aka docker.io. So ubuntu is the same as docker.io/library/ubuntu.
Thus, you need to have the name so it knows which image registry server to talk to.