If you have three layered development structures (local dev, remote staging, remote production) like me, you want to search engines index your staging server. It is easy to prevent search engines from indexing your Nginx
web server.
add_header X-Robots-Tag "noindex, nofollow, nosnippet, noarchive";
Add the line above in the server block virtualhost
file and Google forget the way to go to your server.