为什么本地登上docker却无法上传镜像？

[root@localhost mynginx]# docker push test/lowan:latest
The push refers to a repository [docker.io/test/lowan]

0d45be5b95d8: Preparing
18568efa7ad4: Preparing
1c53295311c1: Preparing
dfcc17ddae9e: Preparing
unauthorized: authentication required