Ever needed to move a container image somewhere? Or add a new tag? There's always the trusty:
1docker pull $src
2docker tag $src $dst
3docker push $dst
But this is inefficient and requires you to download the entire image and maybe upload it again if it's to a different registry.
Instead, you could use skopeo:
1skopeo copy docker://$src docker://$dst
This is a single command and only needs to operate on the image manifests, you can pass image layers between registries directly.
How?
docker image manifests
support a urls field for retrieving layers from a remote,
so you can move images between datacenters
without passing it through your own shitty network.