If you are in process of installing the NRPE daemon as an xinetd service for Nagios monitoring capabilities you may run across this error in /var/log/messages.
If you have started xinetd by typing the following:
shell# /etc/init.d/xinetd start
but you do not see the NRPE service listening by using netstat:
shell# netstat -an | grep 5666
then check /var/log/messages to see if an error similar to the following is in the log file:
xinetd: service/protocol combination not in /etc/services: nrpe/tcp
If so all you need to do is edit /etc/services and add the following line right above the cvsup entries.
nrpe 5666/tcp # NRPE
After this line is added restart xinetd and verify the 5666 port is now open. You should be good to go.
Check out the below book to learn more about lknix system administration.