I had a problem where I couldn’t restart a server powered by Nginx after making a lot of startup configuration changes.
The error I had was
==== AUTHENTICATION COMPLETE === Job for nginx.service failed because the control process exited with error code. See "systemctl status nginx.service" and "journalctl -xe" for details.
Simply run this command
sudo nginx -t -c /etc/nginx/nginx.conf
I was returned
nginx: [emerg] a duplicate default server for 0.0.0.0:80 in /etc/nginx/sites-enabled/test:17 nginx: configuration file /etc/nginx/nginx.conf test failed