Nagios 3 Monitoring of a Linux Box

by Mike on December 15, 2008

in Nagios

The purpose of this is to be able to place the nrpe daemon on a remote Linux machine and be able to monitor specific internal aspects of the server that you would not normally be able to get access to.

You will need to become root and create the user nagios with a password.

# useradd nagios

# passwd nagios

On the remote host you must install the plugins for Nagios.

#apt-get install nagios-plugins
#apt-get install nagios-nrpe-plugin
#apt-get install nagios-nrpe-server

Edit the /etc/nagios/nrpe.cfg
Change your allowed_hosts address to reflect the nagios monitoring server.

allowed_hosts=192.168.5.180

This IP Address must match the IP Address of your Nagios monitoring server.

The basic plugins that are running for you initially are these listed below.

command[check_users]=/usr/lib/nagios/plugins/check_users -w 5 -c 10
command[check_load]=/usr/lib/nagios/plugins/check_load -w 15,10,5 -c 30,25,20
command[check_hda1]=/usr/lib/nagios/plugins/check_disk -w 20 -c 10 -p /dev/hda1
command[check_zombie_procs]=/usr/lib/nagios/plugins/check_procs -w 5 -c 10 -s Z
command[check_total_procs]=/usr/lib/nagios/plugins/check_procs -w 150 -c 200

Change ownership on the /etc/nagios/nrpe.cfg file so that nagios is able to read the file.

chown nagios /etc/nagios/nrpe*

Set up the Firewall
The ufw firewall, Uncomplicated Firewall, is a little tricky.  In the example the remote server being monitored is 192.168.5.178 and the nagios server that is doing the monitoring is 192.168.5.180.

# ufw allow proto tcp from 192.168.5.180 to 192.168.5.178 port 5666
Rules updated
# ufw allow proto tcp from 192.168.5.178 to 192.168.5.180
Rules updated
# ufw enable
Firewall started and enabled on system startup
# ufw status
Status: loaded

To                         Action  From
–                         ——  —-
192.168.5.180/tcp          ALLOW   192.168.5.178/tcp
192.168.5.178 5666/tcp     ALLOW   192.168.5.180

This completes the basic configuration of the host that you will monitor.

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