RedHat系のOSで下記のようなエラーが出てnginxが起動しない時の話。

nginx[89735]: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx[89735]: nginx: [emerg] bind() to 0.0.0.0:4500 failed (13: Permission denied)
nginx[89735]: nginx: configuration file /etc/nginx/nginx.conf test failed
systemd[1]: nginx.service: Control process exited, code=exited, status=1/FAILURE