Repository, name and tag concepts

[th-hummel]

Hello,

I'm trying to figure out (podman) concepts of repository, name and tag which does not seem to be as trivial as it may seem:

I took a look at different documents, including image and distribution OCI specs and this Redhat document.

My first understanding was that basically naming could be broken down like this:

registry/namespace/subnamespace/img_name:tag

which is I think what anyone does when actually using images and running containers.

For a podman image list output looks like this:

REPOSITORY                           TAG         IMAGE ID      CREATED       SIZE
localhost/prod/rhel88                1           be5c1c3c5070  20 hours ago  1.96 GB

I'd tend to consider that image name is rhel88, tag is 1 and namespace is either localhost/prod (or just prod ?)

But I'm not so sure as I also notice the following facts:

1. image "name" does not seem to be a thing in OCI spec
2. repository does not seem to be defined in OCI spec
3. however it obviously exists (as shown above) in podman
4. and could be listed with a command like this :

# podman image list --format '{{.Repository}}' prod/rhel88:1
localhost/prod/rhel88

5. but through Python API the repository concept does not seem to be listable, although it is required for the image.tag() method
6. besides, names listed as repository via podman command line seems to be listed as tags via the Python API (through the image.tags member), so this would differ from the concept of tag as the suffix after the : and listed in the TAG column of image list command
7. OCI seems to define tag as a human readable reference to image manifest, so API would seem to be correct for that matter ?

Can you help me clarify what's what in which context

A simple example would be : suppose you want, with the API to move the latest tag to a particular image version : you'd have to extract the repository first from your target image full name (let's say localhost/prod/rhel88:2) in order to make it the first parameter of the tag() method. But this repository name, if I'm correct, would only be computable through the tag member but which a) may llist multiple items and b) include the :xxx "tag"

Thanks for your help

--
Thomas HUMMEL

[th-hummel]

I forgot to mention the names field in the images.json file, which seem to also be the list of tags (with localhost considered not part of the tag ?)