sudo service nginx restart
Redirecting to /bin/systemctl restart nginx.service
Job for nginx.service failed because the control process exited with error code. See "systemctl status nginx.service" and "journalctl -xe" for details.
systemctl status nginx.service
● nginx.service - The nginx HTTP and reverse proxy server
Loaded: loaded (/usr/lib/systemd/system/nginx.service; disabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Mon 2019-05-13 17:15:38 CST; 7min ago
Process: 24060 ExecStart=/usr/sbin/nginx (code=exited, status=1/FAILURE)
Process: 24056 ExecStartPre=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS)
Process: 24054 ExecStartPre=/usr/bin/rm -f /run/nginx.pid (code=exited, status=0/SUCCESS)
ps aux | grep nginx
root 23885 0.0 0.0 125100 2164 ? Ss 16:57 0:00 nginx: master process /usr/sbin/nginx
nginx 23886 0.0 0.0 125620 3636 ? S 16:57 0:00 nginx: worker process
nginx 23887 0.0 0.0 125620 3636 ? S 16:57 0:00 nginx: worker process
yak 24099 0.0 0.0 112708 976 pts/7 S+ 17:26 0:00 grep --color=auto nginx

sudo /usr/sbin/nginx
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] still could not bind()