nginx lỗi restart: [domain] Failed to start A high performance web server*** and a reverse proxy server.****

 root@zabbix:/home/appliance# systemctl status nginx.service

nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Wed 2018-07-25 18:33:26 UTC; 1min 27s ago
  Process: 30040 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=1/FAILURE)
  Process: 30037 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0/SUCCESS)

Jul 25 18:33:25 zabbix nginx[30040]: nginx: [emerg] listen() to [::]:80, backlog 511 failed (98: Address already in use)
Jul 25 18:33:25 zabbix nginx[30040]: nginx: [emerg] listen() to 0.0.0.0:80, backlog 511 failed (98: Address already in use)
Jul 25 18:33:25 zabbix nginx[30040]: nginx: [emerg] listen() to [::]:80, backlog 511 failed (98: Address already in use)
Jul 25 18:33:26 zabbix nginx[30040]: nginx: [emerg] listen() to 0.0.0.0:80, backlog 511 failed (98: Address already in use)
Jul 25 18:33:26 zabbix nginx[30040]: nginx: [emerg] listen() to [::]:80, backlog 511 failed (98: Address already in use)
Jul 25 18:33:26 zabbix nginx[30040]: nginx: [emerg] still could not bind()
Jul 25 18:33:26 zabbix systemd[1]: nginx.service: Control process exited, code=exited status=1

Jul 25 18:33:26 zabbix systemd[1]: *******Failed to start A high performance web server*** and a reverse proxy server.****

Jul 25 18:33:26 zabbix systemd[1]: nginx.service: Unit entered failed state.
Jul 25 18:33:26 zabbix systemd[1]: nginx.service: Failed with result 'exit-code'.

Hoặc
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)

========>
For me this error was caused by a default nginx site already on port 80. Removing default site worked

sudo rm /etc/nginx/sites-enabled/default

sudo service nginx restart