Pushing an image with existing tag

[ueoeae]

How do you handle a crane push of an image if the tag already exists in the registry? The push still happens if the tag exists, and overwrites previous push/tag.

[imjasonh]

In this case the push should still succeed and the tag should point to the newly pushed image.

This matches the behavior of docker push, etc.

Depending on the registry, the previous image may still be available by digest, or by any other tags it still has pointing to it.

[ueoeae]

In this case the push should still succeed and the tag should point to the newly pushed image.

This matches the behavior of docker push, etc.

Depending on the registry, the previous image may still be available by digest, or by any other tags it still has pointing to it.

Would you know of a possibility to check if the used tag already exists so that a push does not take place unless the tag is unique?

[imjasonh]

You can check for the existence of an image at a tag with crane digest, which will fail if the tag doesn't exist. Something like:

crane digest registry.com/my/image:tag && echo "tag exists" && exit 1
crane push image.tar registry.com/my/image:tag

If registry.com/my/image:tag exists then it won't be pushed to.

Beware there's a possible race condition, if you check for the existence of a tag then push to it; another process can push to that tag in the meantime. At this time there isn't a "push to this tag only if it doesn't exist yet" option, though enabling this across registries is being discussed in OCI: opencontainers/distribution-spec#250

[imjasonh]

Closing this, please reply if this didn't answer your question.