root@optp1277:~# systemctl status nginx
● nginx.service - nginx - high performance web server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled)
   Active: failed (Result: exit-code) since Sat 2018-01-20 14:14:49 CET; 54s ago
     Docs: http://nginx.org/en/docs/
  Process: 2729 ExecStart=/usr/sbin/nginx -c /etc/nginx/nginx.conf (code=exited, status=1/FAILURE)
  Process: 2725 ExecStartPre=/usr/sbin/nginx -t -c /etc/nginx/nginx.conf (code=exited, status=0/SUCCESS)

Jan 20 14:14:46 optp1277 nginx[2725]: nginx: configuration file /etc/nginx/nginx.conf test is successful
Jan 20 14:14:46 optp1277 nginx[2729]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Jan 20 14:14:47 optp1277 nginx[2729]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Jan 20 14:14:47 optp1277 nginx[2729]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Jan 20 14:14:48 optp1277 nginx[2729]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Jan 20 14:14:48 optp1277 nginx[2729]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Jan 20 14:14:49 optp1277 nginx[2729]: nginx: [emerg] still could not bind()
Jan 20 14:14:49 optp1277 systemd[1]: nginx.service: control process exited, code=exited status=1
Jan 20 14:14:49 optp1277 systemd[1]: Failed to start nginx - high performance web server.
Jan 20 14:14:49 optp1277 systemd[1]: Unit nginx.service entered failed state.