Nagios: Monitoring a custom

I'm using Debian 6 and Nagios3.

Sometimes, it becomes essential to monitor a non-standard port in Nagios. An example may be monitoring TCP port 5555.

Before we start, there is something that needs to be known- 
  • Nagios has included a bunch of custom command. The commands are defined in the directory /etc/nagios-plugins/config/
  • The executable for these defined commands are located in /usr/lib/nagios/plugins/
Since we want to monitor a custom TCP port, we will use Nagios's existing TCP checking tool. We will just add port 5555 as an argument to the command.

  • Checking

root@dragonfly:~# /usr/lib/nagios/plugins/check_tcp -H -p 5555
TCP OK - 0.001 second response time on port 55|time=0.000502s;;;0.000000;10.000000

So, we can certainly conclude that port 5555 is accessible.

  • Defining the command
vim /etc/nagios-plugins/config/tcp_udp.cfg


define command{
     command_name check_tcp_5555
     command_line $USER1$/check_tcp -h $HOSTADDRESS$ -p 5555 -4

  • Defining a host to use the command
root@dragonfly:~#vim /etc/nagios3/conf.d/localhost_nagios2.cfg

define host{
        use                     linux-hosts
        host_name               bee
        alias                   bee

define host{
        use                     linux-hosts
        host_name               dragonfly
        alias                   dragonfly

define hostgroup{
        hostgroup_name  linux-hosts
        alias           Linux Hosts
        members         dragonfly, bee;

define service{
        use                             generic-service         ; Name of service template to use
        hostgroup_name                  linux-hosts
        service_description             Check Host
        check_command                   check-host-alive
        check_command                   check_tcp_5555        ; our customized command

  • Restarting the service
Finally, time to restart the nagios service.

root@dragonfly:~# /etc/init.d/nagios3 restart

Nagios should now be monitoring TCP port 5555. We can check it out by going to the Nagios page in the browser ^_^.

If it doesn't, check out the Nagios log at /var/log/nagios3/nagios.log.

Hope this helps.