Adding new services

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Nagios services are configured using plugins from /usr/lib64/nagios/plugins folder. Various executables present here such as check_dns, check_tcp, etc. can be used to configure various types of service checks.

The command definitions for services are mentioned in /etc/nagios/objects/commands.cfg file. Example command definition is:

define command{
        command_name    check_tcp
        command_line    $USER1$/check_tcp -H $HOSTADDRESS$ -p $ARG1$ $ARG2$
        }

This means that if service_command is specified as "check_tcp!636!-S" then it would result into running "check_tcp -H <Address> -p 636 -S" where <Address> would come from host_name specified as part of service definition. For every host_name there is corresponding host entry with address for given host.

Thus if we want to add checks for dns using check_dns plugin then we can add following configuration to command.cfg file:

define command{
        command_name    check_dns
        command_line    $USER1$/check_dns -s $HOSTADDRESS$ -H $ARG1$ $ARG2$
        }

After this the service definition to check DNS resolution from a DNS server may look like:

define service{
use generic-service;
host_name ns1
service_description DNS-www.google.co.in
check_command check_dns!www.google.co.in
notifications_enabled 1
}

define service{
use generic-service;
host_name ns1
service_description DNS-sbarjatiya.com
check_command check_dns!sbarjatiya.com
notifications_enabled 1
}

to make nagios periodically verify that DNS is able to resolve both Internet addresses (www.google.co.in) as well as local domains (sbarjatiya.com).

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