Nagios is a popular networking monitoring software used by various hosting providers including Tech With Us servers,

Designed with scalability and flexibility in mind, Nagios gives you the peace of mind that comes from knowing your organization’s business processes won’t be affected by unknown outages.

Nagios is a powerful tool that provides you with instant awareness of your organization’s mission-critical IT infrastructure. Nagios allows you to detect and repair problems and mitigate future issues before they affect end-users and customers.

By using Nagios, you can:

• Plan for infrastructure upgrades before outdated systems cause failures
• Respond to issues at the first sign of a problem
• Automatically fix problems when they are detected
• Coordinate technical team responses
• Ensure your organization’s SLAs are being met
• Ensure IT infrastructure outages have a minimal effect on your organization’s bottom line
• Monitor your entire infrastructure and business processes

Today i will be giving a quick tutorial about how to install Nagios for monitoring your servers easily from one Nagios installed VPS/Dedicated Server.

Basically Nagios contains 3 monitoring :

• Local disk space usage
• Local system load
• An external website

Whenever there is a problem or recovery with any of the above, Nagios will alert you right away via email!

So Lets Get Started,

Enabling RPMForge repository

For 32 bit machines use this commands:

For 64 bit machines use this commands:

Installing And Configuring Nagios

Install Nagios and Nagios plugins.

Configure startup services.
Use ntsysv and mark nagios to be started when the computer starts. Alternatively you can use the command chkconfig to configure startup services.

Start the nagios daemon.

Let’s start configuring Nagios. All the configuration object files are stored in the directory /etc/nagios/objects/. Each configuration object file ends with .cfg extension. The first thing you have to do is edit your contact information.

Edit the file /etc/nagios/objects/contacts.cfg to set your email address.

define contact{
        contact_name                    tharunpkarun             ; Short name of user
        use                             generic-contact         ; Inherit default values from generic-contact template (defined above)
        alias                           Tharun P Karun            ; Full name of user

        email                           alerts@techwithus.com        ; <<***** CHANGE THIS TO YOUR EMAIL ADDRESS ******
        }

Replace “tharunpkarun” with your desired username, replace “Tharun P Karun” with your Full Name & Replace “alerts@techwithus.com” with your email address / email address for recieveing alerts.

By default, a localhost host object is defined. You can find the details in the file /etc/nagios/objects/localhost.cfg. If you observe, Nagios is configured to monitor PING, Root Partition, Current Users, Total Processes, Current Load, Swap Usage, SSH and HTTP on the local machine. At the beginning of the article, I said we are going to monitor three services. But hey, you got more for free! Each check_command relates to a plugin. For example, check_disk relates to the plugin /usr/lib/nagios/plugins/check_disk. On 64 bit machines, the path to Nagios plugins is /usr/lib64/nagios/plugins.

Run the command manually to see how it works.

In the above command, -w switch indicates the warning level and -c switch indicates the critical level. Increase or decrease the warning and critical argument values and observe the status. In the configuration file the arguments are declared using the exclamatory mark separator.

Edit the values in /etc/nagios/objects/localhost.cfg file

To get an alert, alter the values and restart nagios daemon. Wait for about 5 minutes.

Here’s the body of a sample notification email I received:

***** Nagios *****

Notification Type: PROBLEM

Service: Root Partition
Host: localhost
Address: 127.0.0.1
State: CRITICAL

Date/Time: Mon Nov 8 00:53:32 IST 2010

Additional Info:

DISK CRITICAL - free space: / 1924 MB (47% inode=92%):

If you did not receive the email, check your mail server logs. Also, you can view the Nagios log at /var/log/nagios/nagios.log.

to debug.