push a

[root@docker1 ~]# docker push sshd:centos

Error response from daemon: You cannot push a "root" repository. Please rename your repository to docker.io/<user>/<repo> (ex: docker.io/<user>/sshd)

[root@docker1 ~]# docker tag docker.io/nginx 127.0.0.1:5000/nginx:latest

[root@docker1 ~]# docker images

REPOSITORY TAG IMAGE ID CREATED SIZE
127.0.0.1:5000/nginx latest ae513a47849c 7 days ago 108.9 MB
docker.io/nginx latest ae513a47849c 7 days ago 108.9 MB
[root@docker1 ~]# docker push 127.0.0.1:5000/nginx:latest
The push refers to a repository [127.0.0.1:5000/nginx:latest]
7ab428981537: Image successfully pushed
82b81d779f83: Image successfully pushed
d626a8ad97a1: Image successfully pushed
Pushing tag for rev [ae513a47849c] on {http://127.0.0.1:5000/v1/repositories/nginx.latest/tags/latest}

You cannot push a "root" repository.