I.Preparation
Install epel and remi repositories. Reference link here Click Here
Make sure Apache , PHP and MySQL have been installed in the server
Reference link here click here
Stop iptables service
# service iptables stop
# chkconfig iptables off
II.Proceeding
1. Setup on server
Install nagios and accessory packages via yum command
# yum -y install nagios nagios-plugins-all nagios-plugins-nrpe nrpe
Start nagios and run it together with the system
# service nagios start
# chkconfig nagios on
Set a password for nagiosadmin user used to login
# htpasswd -c /etc/nagios/passwd nagiosadmin
If you don't use nagiosadmin user, you need to change and re-configure the file /etc/nagios/cgi.cfg
Here you can visit http://IP-vps/nagios