Nagios Part 4 | Getting EMail Alerts & Notifications for Nagios Events

This is a multi-part series of Nagios articles all focused on configuring a complete Nagios monitored network. Find all related articles here.

Nagios has the ability to send emails to contacts (email addresses) and groups of contacts when events occur. This article demonstrates how contacts get notified.

The file we’re going to focus on is the “/etc/nagios/objects/contacts.cfg” file. The default contacts file looks like this:

define contact{
        contact_name                    nagiosadmin		; Short name of user
	use				generic-contact		; Inherit default values from generic-contact template (defined above)
        alias                           Nagios Admin		; Full name of user
        email                           nagios@localhost	; <<***** CHANGE THIS TO YOUR EMAIL ADDRESS ******
        }
define contactgroup{
        contactgroup_name       admins
        alias                   Nagios Administrators
        members                 nagiosadmin
        }

Here’s my Nagios “contacts” file:

define contactgroup{
        contactgroup_name       admins
        alias                   Nagios Administrators
        members                 webadmin,mailadmin
        }

define contact{
        contact_name                    webadmin
	use				generic-contact	
        alias                           Web Admin
        email                           [email protected]
        service_notification_commands   notify-service-by-email
        host_notification_commands      notify-host-by-email
        }
define contact{
        contact_name                    mailadmin
	use				generic-contact	
        alias                           Mail Admin
        email                           [email protected]
        service_notification_commands   notify-service-by-email
        host_notification_commands      notify-host-by-email
        }

We need to make a change to our “/etc/nagios/servers/clients.cfg” file to specify who (or what groups of contacts) should be notified when events occur. Here’s a sample of how we modify a “service”:

define service{
        use                     generic-service
        hostgroup_name          snmp-servers
        service_description     CPU 5 Minute Load
        check_command           check_snmp!-C public -o 1.3.6.1.4.1.2021.10.1.3.2 -P 2c
        contact_groups          admins
}

Notice the “contact_groups admins” section.

The above shows that the “admins” group will get notified if there is an event effecting the service “CPU 5 Minute Load”. Do the same for each service that you want to monitor.

Still in the “/etc/nagios/servers/clients.cfg” file, we need to add contacts to “host” entries too. Here’s a sample of how we do that. The only difference here is that i don’t want a group to be contacted if there is a problem with a specific host, i want to notify a specific person (via email).

define host{
        use                             linux-server
        host_name                       www.example.com
        alias                           www.example.com
        address                         www.example.com
        max_check_attempts              5
        check_period                    24x7
        notification_interval           30
        notification_period             24x7
        contacts                        webadmin
}

Notice the “contacts webadmin” section.

The above shows that the contact (not a group but a specific contact) “webadmin” will be notified if there is an event effecting this host. Do the same with the other hosts and specify the host or hostgroup that should be notified of an event.

Once your changes have been made, restart Nagios. You can test notifications via the Nagios web portal. Follows these steps:

1. Click “Services” in the left menu. Click on any failed service (yellow) in the main area.
2. Click “Send custom service notification” in the right menu.
3. Enter a custom “comment” and click the “Commit” button.

Check your inbox for your notification email. If you don’t get it, check your server logs to see if there is a system issue on the Nagios server.

References:

• https://arkit.co.in/creating-nagios-contacts/