Hey John @babb.sdn ,
As mentioned in dockerhub it is not possible to mirror a private registry in docker.
It’s currently not possible to mirror another private registry. Only the central Hub can be mirrored.
Whenever you use Nexus as a hosted or proxy or group registry for docker it is considered as a private registry and you can use it by referring explicitly (e.g. docker pull dkr-nxs-reg/libraty/image:tag )
Reza