For Redhat 5.4 or CentOS 5.4

can just add rpmforge repository ..

then do the following to the monitoring host.

yum install nagios-nrpe nagios-nrpe-plugins -y

which pretty much covered in previous post regarding nagios installation.
only need to ammend the file at

 vi /etc/nagios/objects/commands.cfg

to add the following..

 
# 'check_nrpe' command definition
define command{
        command_name check_nrpe
        command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
        }

and for each remote server that you want to monitor.
Need to add some package into it.

yum install nagios-nrpe -y

edit the /etc/nagios/nrpe.cfg

find the line started with allowed_hosts,
append the monitoring server ip accordingly .. so that it can access to the remote host with SSL successfully.

allowed_hosts=192.168.19.31

you can also changed the following code
to suit your need.

# The following examples use hardcoded command arguments...
 
command[check_users]=/usr/lib64/nagios/plugins/check_users -w 5 -c 10
command[check_load]=/usr/lib64/nagios/plugins/check_load -w 15,10,5 -c 30,25,20
command[check_hda1]=/usr/lib64/nagios/plugins/check_disk -w 20% -c 10% -p /dev/hda1
command[check_logvol00]=/usr/lib64/nagios/plugins/check_disk -w 20% -c 10% -p /dev/mapper/VolGroup01-LogVol00
command[check_zombie_procs]=/usr/lib64/nagios/plugins/check_procs -w 5 -c 10 -s Z
command[check_total_procs]=/usr/lib64/nagios/plugins/check_procs -w 450 -c 500
command[check_swap]=/usr/lib64/nagios/plugins/check_swap -w 20 -c 10

then just need to start it.

/etc/init.d/nrpe start
chkconfig nrpe on

then can test.. with something like this
from the monitoring server.

/usr/lib64/check_nrpe -H 192.168.19.203 check_load
 
/usr/lib64/nagios/plugins/check_nrpe -H 192.168.19.216 -c "check_total_procs"

oh well..

that’s pretty much of it.

then can have something like this at the end..

p/s : .. there might more underneath feature that can be added..
let’s see if someone can come up with enough time to play with it.. 😎