The Geek Stuff posted 6 Nagios command line options explained with examples
This article explains various command line options that are available for the nagios command.6 Nagios Command Line Options Explained with Examples
1. Start Nagios Daemon Using nagios -d
Typically you would execute “service nagios start” to start the Nagios daemon, which really calls the /etc/rc.d/init.d/nagios script.