1)
docker tag nginx:latest unix1998/repo_2019:nginx_test1
nginx:latest is an image in your local server, can be any other
unix1998/repo_2019:nginx_test1
unix1998 is user id in dcoekr hub,
repo_2019 is repo name created in unix1998 @ docker hub
2) docker push unix1998/repo_2019:nginx_test1
will be OK
