How To Install Nagios on Debian 9

Install Nagios on Debian 9

In this tutorial, we will show you how to install Nagios on your Debian 9 Stretch. For those of you who didn’t know, Nagios will monitor servers, switches, applications and services. It alerts the System Administrator when something went wrong and also alerts back when the issues have been rectified. Resources that can be monitored include CPU, memory and disk space loads, log files, temperature or hardware errors. It can monitor various parameters and problems for services like HTTP, SMTP, DNS, and with the help of plugins, it can be highly extended. Nagios core was originally designed to run under Linux, although it should work under most other unices as well.

This article assumes you have at least basic knowledge of Linux, know how to use the shell, and most importantly, you host your site on your own VPS. The installation is quite simple and assumes you are running in the root account, if not you may need to add ‘sudo’ to the commands to get root privileges. I will show you through the step by step installation Nagios open source monitoring tool on a Debian 9 (Stretch) server.

Install Nagios on Debian 9 Stretch

Step 1. Before we install any software, it’s important to make sure your system is up to date by running these following apt-get commands in the terminal:

Step 2. Install LAMP (Linux, Apache, MariaDB and PHP) server.

A Debian 9 LAMP server is required. If you do not have LAMP installed, you can follow our guide here. Also, install the dependencies for Nagios:

Step 3. Create users and groups for Nagios.

Now create a new nagios user account and set up a password to this account:

Step 4. Installing Nagios and plugins.

The first thing to do is to go to Nagios’s download page and download the latest stable version of Nagios, At the moment of writing this article it is version 4.3.2:

Perform the below steps to compile the Nagios from the source code:

Next steps, Download latest nagios-plugins source and install using the following commands:

Compile and install the plugins:

Step 5. Configure Nagios.

Edit the /usr/local/nagios/etc/objects/contacts.cfg config file with your favourite editor and change the email address associated with the nagiosadmin contact definition to the address you’d like to use for receiving alerts.

Change the email address field to receive the notification:

Step 6. Configure Nagios Web Interface.

Now create Nagios apache2 configuration file:

Edit the following lines if you want to access nagios administrative console from a particular IP series, Here, I want to allow nagios administrative access from series only:

Enable Apache’s rewrite and cgi modules:

Configure Apache authentication:

We need to set up the password for the user nagiosadmin. This username will be used to access the web interface so it is important to remember the password that you will input here. Set the password running the following command and enter the password twice:

Restart Apache for the changes to take effect:

Step 7. Verify and Start Nagios service.

Next, we have to make Nagios start at boot time, so first verify that the configuration file has no errors running the following command:

Step 8. Configure the firewall for Nagios.

Configure the firewall open port 80 to enable access to the Nagios:

Step 9. Accessing Nagios.

Nagios will be available on HTTP port 80 by default. Open your favourite browser and navigate to or http://server-ip/install.php and complete the required steps to finish the installation. When prompted for username and password you will introduce the username “nagiosadmin” and the password that you entered in step 6.

Install Nagios on Debian 9

Congratulations! You have successfully installed Nagios. Thanks for using this tutorial for installting Nagios monitoring tool in Debian 9 (Stretch) systems. For additional help or useful information, we recommend you to check the official Nagios web site.

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