Installing and Setting Up Nagios on CentOS Stream 9: A Practical Guide

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 :

Table of Contents

1. Introduction
2. Prerequisites
3. Step 1: Update the System
4. Step 2: Install Essential Packages
5. Step 3: Create Nagios User and Group
6. Step 4: Install Nagios Core
7. Step 5: Install Nagios Plugins
8. Step 6: Configure the Web Interface
9. Step 7: Start and Enable Services
10. Step 8: Open Firewall Ports
11. Step 9: Access the Nagios Dashboard
12. Step 10: Verify Your Setup
13. Conclusion

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.

1. Introduction

Nagios Core is a robust, open-source monitoring solution that keeps tabs on your servers, services, and network devices. In this guide, you’ll walk through installing Nagios Core on CentOS Stream 9, configuring its web interface, and opening necessary firewall ports for access.

2. Prerequisites

Before beginning, make sure you have:

• A server running CentOS Stream 9
• A user account with sudo privileges (avoid root)
• Basic familiarity with the Linux command line

3. Step 1: Update the System

Kick off with a fresh update to ensure your software packages are current:

sudo dnf update -y

4. Step 2: Install Essential Packages

Nagios Core requires HTTPD, PHP, and development tools. Install them with:

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

You may also add packages like gd, perl, or others depending on your setup.

5. Step 3: Create Nagios User and Group

Nagios needs its own user and command group for security and execution:

sudo useradd nagios
sudo groupadd nagcmd
sudo usermod -aG nagcmd nagios
sudo usermod -aG nagcmd apache

6. Step 4: Install Nagios Core

Download and extract the latest Nagios Core:

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 compile and install:

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

7. Step 5: Install Nagios Plugins

Plugins are essential for monitoring. Set them up with:

cd /tmp
wget https://nagios-plugins.org/download/nagios-plugins-2.4.6.tar.gz
tar zxvf nagios-plugins-2.4.6.tar.gz
cd nagios-plugins-2.4.6
./configure --with-nagios-user=nagios --with-nagios-group=nagcmd
make
sudo make install

8. Step 6: Configure the Web Interface

Set up access to Nagios’ web UI:

sudo make install-webconf
sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Provide a password when prompted—you’ll use these credentials later.

9. Step 7: Start and Enable Services

Enable and launch Nagios and Apache on boot:

sudo systemctl enable nagios
sudo systemctl start nagios
sudo systemctl enable httpd
sudo systemctl start httpd

10. Step 8: Open Firewall Ports

Allow HTTP traffic so you can access Nagios remotely:

sudo firewall-cmd --permanent --add-port=80/tcp
sudo firewall-cmd --reload

11. Step 9: Access the Nagios Dashboard

Point your browser to:

http://<your-server-IP>/nagios

Log in using:

• Username: nagiosadmin
• Password: the one you created earlier

You should now see Nagios’ main monitoring interface.

12. Step 10: Verify Your Setup

Check the health and status of your hosts and services. If everything appears, congratulations! Your Nagios Server is up and running.

13. Conclusion

You’ve now completed the installation of Nagios Core on CentOS Stream 9. From updating your system to logging into the Nagios dashboard, this guide has covered the essentials. You’re now ready to expand your monitoring setup with additional hosts, services, and alerting features.