If launching the nagios web interface, you encountered error like "Return code of 127 for check of service 'HTTP' on host 'localhost' was out of bounds. Make sure the plugin you're trying to run actually exists."
From the error itself, your installation of nagios-plugins has issues. To resolve the problems, make sure you install
# yum install nagios-plugins-all
(You should see 55+ plugin packages being installed)
For other readings on Nagios, see
