Quick Guide to Installing and Configuring Nagios on CentOS Stream 9

In this guide, we’ll go through the steps needed to install and configure Nagios on CentOS Stream 9. Nagios is a widely used open-source monitoring tool that helps system administrators monitor network devices, services, and host resources. The Nagios installation on CentOS Stream 9 is as follows :

1. Update Your System
2. Install Required Packages
3. Create a Nagios User and Group
4. Download and Install Nagios Core
5. Install and Configure Nagios Plugins
6. Configure Nagios Web Interface
7. Start Nagios
8. Open the Firewall
9. Access the Nagios Web Interface
10. Verify Configuration and Start Monitoring

Nagios is a powerful, open-source IT infrastructure monitoring system widely used to monitor networks, servers, applications, and services. It’s particularly popular among system administrators for its extensive features, flexibility, and reliability, making it ideal for large-scale IT environments where maintaining uptime and performance is crucial.

Prerequisites

Before you begin, make sure you have:

• A server running CentOS 9
• A non-root user with sudo privileges
• Basic understanding of the command line

Let’s get started!

Step 1: Update Your System

To ensure all packages are up to date, run:

$ sudo dnf update -y

This command will download and install any available updates.

Step 2: Install Required Packages

Nagios requires several dependencies to run properly. Install them with the following command:

$ sudo dnf install httpd php gcc glibc glibc-common wget unzip -y

This will install Apache (httpd), PHP, and additional libraries.

Step 3: Create a Nagios User and Group

Nagios needs its own user and group. Create them by running:

$ sudo useradd nagios
$ sudo usermod -aG nagios apache

Step 4: Download and Install Nagios Core

Next, download the latest Nagios Core package from the official site:

$ cd /tmp
$ wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.4.6.tar.gz
$ tar -zxvf nagios-4.4.6.tar.gz
$ cd nagios-4.4.6

Now, configure and compile Nagios:

$ sudo ./configure --with-command-group=nagios
$ sudo make all
$ sudo make install
$ sudo make install-init
$ sudo make install-config
$ sudo make install-commandmode

Step 5: Install and Configure Nagios Plugins

Download the Nagios plugins, which provide additional checks and features:

$ cd /tmp
$ wget https://nagios-plugins.org/download/nagios-plugins-2.3.3.tar.gz
$ tar -zxvf nagios-plugins-2.3.3.tar.gz
$ cd nagios-plugins-2.3.3

Then configure and compile the plugins:

$ sudo ./configure --with-nagios-user=nagios --with-nagios-group=nagios
$ sudo make
$ sudo make install

Step 6: Configure Nagios Web Interface

To access Nagios from a web browser, you’ll need to configure Apache:

1. Create a Nagios Admin User:

$ sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

When prompted, enter a password for the user.

2. Configure Apache: Enable the Nagios configuration file in Apache:

$ sudo ln -s /usr/local/nagios/etc/nagios.conf /etc/httpd/conf.d/

3. Restart Apache:

$ sudo systemctl restart httpd

Step 7: Start Nagios

Enable and start the Nagios service:

$ sudo systemctl enable nagios
$ sudo systemctl start nagios

Step 8: Open the Firewall

Allow HTTP traffic so you can access the Nagios web interface:

$ sudo firewall-cmd --zone=public --add-service=http --permanent
$ sudo firewall-cmd --reload

Step 9: Access the Nagios Web Interface

Open your web browser and go to:

http://your_server_ip/nagios

Log in using the credentials for nagiosadmin.

Step 10: Verify Configuration and Start Monitoring

To confirm that everything is working, Nagios provides a configuration verification tool:

$ sudo /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

After verifying, restart Nagios to load the configuration:

$ sudo systemctl restart nagios

Conclusion

Congratulations! You’ve successfully installed and configured Nagios on CentOS 9. Now, you’re ready to start monitoring hosts, services, and network devices. For advanced monitoring setups, explore adding custom plugins or configuring alerts for more granular control.