March 27, 2025

How to Monitor Rocky Linux 9 Using NCPA with Nagios XI

Ayub Huruse

IT Specialist

Efficient server monitoring is crucial for maintaining optimal system performance and minimizing downtime. The Nagios Cross-Platform Agent (NCPA) is a lightweight, agent-based tool that simplifies real-time monitoring for Linux systems like Rocky Linux 9. Unlike SNMP, NCPA leverages a secure, RESTful API to collect detailed system metrics, making it a powerful and secure monitoring solution for integration with Nagios XI.

This guide walks you through the installation and configuration process of NCPA on Rocky Linux 9, enabling comprehensive system monitoring through Nagios XI.

Prerequisites

Before proceeding, ensure you have:

A Rocky Linux 9 system with root or sudo privileges
Nagios XI installed and accessible, with the NCPA Wizard enabled
A stable internet connection for package downloads
SELinux set to enforcing or permissive (check with getenforce; adjust if needed)

Step 1: Install the Nagios Repository

Install the Nagios repository to access NCPA packages:

sudo rpm -Uvh https://repo.nagios.com/nagios/9/nagios-repo-9-1.el9.noarch.rpm
sudo yum update -y

sudo rpm -Uvh https://repo.nagios.com/nagios/9/nagios-repo-9-1.el9.noarch.rpm
sudo yum update -y

Then refresh the package list:

sudo dnf clean all
sudo dnf update -y

sudo dnf clean all
sudo dnf update -y

Step 2: Install NCPA on Rocky Linux 9

Install the NCPA agent:

sudo dnf install ncpa -y

sudo dnf install ncpa -y

Verify the installation:

rpm -q ncpa

rpm -q ncpa

Expected output: ncpa-<version>.el9.x86_64

Step 3: Configure NCPA

Edit the configuration file to set your API token:

sudo nano /usr/local/ncpa/etc/ncpa.cfg

sudo nano /usr/local/ncpa/etc/ncpa.cfg

Locate:

community_string = mytoken

community_string = mytoken

Replace with a strong, unique value:

community_string = Str0ngT0k3n2025

community_string = Str0ngT0k3n2025

Replace mytoken with a secure token like Str0ngT0k3n2025. Save and exit.

Step 4: Enable and Start NCPA Service

Enable and start the NCPA service:

sudo systemctl enable ncpa
sudo systemctl start ncpa
sudo systemctl status ncpa

sudo systemctl enable ncpa
sudo systemctl start ncpa
sudo systemctl status ncpa

Ensure the output shows active (running).

Step 5: Configure Firewall Rules

Allow traffic to NCPA on port 5693:

sudo firewall-cmd --zone=public --add-port=5693/tcp --permanent
sudo firewall-cmd --reload

sudo firewall-cmd --zone=public --add-port=5693/tcp --permanent
sudo firewall-cmd --reload

Check the rule:

sudo firewall-cmd --list-ports

sudo firewall-cmd --list-ports

Step 6: Test NCPA Installation

Visit the NCPA web interface:

https://<RockyLinux9-IP>:5693/

https://<RockyLinux9-IP>:5693/

Accept the certificate warning. Enter your API token to log in.

Step 7: Add Rocky Linux 9 Host to Nagios XI Using NCPA Wizard

1. Log into Nagios XI.

2. Go to Configure > Configuration Wizards.

3. Choose NCPA.

4. Enter the Rocky Linux 9 server’s IP and token.

5. Click Next, choose system metrics (CPU, memory, disk, etc.).

6. Complete the wizard and apply the configuration.

Common Issues & Fixes

NCPA Not Running

Check logs:

sudo journalctl -u ncpa --no-pager | tail -20

sudo journalctl -u ncpa --no-pager | tail -20

Restart NCPA:

sudo systemctl restart ncpa

sudo systemctl restart ncpa

Host Appears Down in Nagios XI

Check firewall:

sudo firewall-cmd --list-ports

sudo firewall-cmd --list-ports

Verify NCPA is running:

sudo systemctl status ncpa

sudo systemctl status ncpa

Incorrect API Token Error

Ensure the token matches ncpa.cfg, then:

sudo systemctl restart ncpa

sudo systemctl restart ncpa

Conclusion

You have successfully installed and configured NCPA on Rocky Linux 9 for monitoring with Nagios XI. This setup allows real-time visibility and proactive performance monitoring.

For further help: