Date: 2008apr5 OS: Linux Q. How do I quickly install Nagios on RedHat/Fedora/CentOS? A. This worked for me:

dnf install nagios nagios-plugins-all htpasswd -c /etc/nagios/passwd nagios-admin <select a password> systemctl start nagios

Browse to:

http://localhost/nagios/

and login with

User: nagios-admin Password: <that you selected above>

You can now customize you setup by editing /etc/nagios/localhost.cfg The plugins are in /usr/lib/nagios/plugins