March 26, 2025

Comprehensive Guide: Monitoring AlmaLinux 9 with NCPA in Nagios XI

Ayub Huruse

The Nagios Cross-Platform Agent (NCPA) is a lightweight, flexible agent that enables centralized monitoring of AlmaLinux 9 from Nagios XI. Whether you’re monitoring CPU, memory, disk, or services, NCPA supports both active checks (pulled by Nagios) and passive checks (pushed via NRDP).

This guide outlines how to install, configure, and connect AlmaLinux 9 with Nagios XI using NCPA 3.x as of March 2025.

Prerequisites

A Nagios XI instance (latest version)
AlmaLinux 9 system (fully updated with sudo dnf update)
Root/sudo access
Port 5693 open between AlmaLinux and Nagios XI
firewalld installed and running

Step 1: Install NCPA on AlmaLinux 9

Option 1: Install via Nagios Repository (Recommended)

Visit https://repo.nagios.com for the latest instructions tailored to RHEL-based systems.

sudo rpm -Uvh https://repo.nagios.com/nagios/9/nagios-repo-9-1.el9.noarch.rpm
sudo dnf install ncpa -y

Option 2: Manual RPM Installation

cd /tmp
wget https://assets.nagios.com/downloads/ncpa/ncpa-latest-1.x86_64.rpm
sudo rpm -ivh ncpa-latest-1.x86_64.rpm

Ensure dependencies like python3 are installed if needed.

Step 2: Configure NCPA Token

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

Edit:

community_string = Str0ngT0k3n2025

Save and exit.

Step 3: Start and Enable NCPA

sudo systemctl restart ncpa
sudo systemctl enable ncpa
sudo systemctl status ncpa

Ensure status is active (running).

Step 4: Open Firewall Port 5693

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

Confirm 5693/tcp is listed.

Step 5: Verify NCPA Installation

Access the web interface:

https://<AlmaLinux-IP>:5693

Accept the certificate warning and log in using your token Str0ngT0k3n2025. The dashboard should show system stats.

Step 6: Add Host to Nagios XI

1. Log in to Nagios XI.

2. Go to Configure > Configuration Wizards > NCPA.

3. Enter:

IP: AlmaLinux IP
Port: 5693
Token: Str0ngT0k3n2025

4. Choose desired checks (CPU, memory, disk, processes).

5. Finish wizard and apply configuration.

Step 7: Optional – Setup Passive Checks (NRDP)

In Nagios XI, go to Admin > Inbound Transfers > NRDP to get the URL and token.
Edit ncpa.cfg:

[passive checks]
%HOSTNAME%|CPU Usage = cpu/percent --warning 60 --critical 80

Restart NCPA:

sudo systemctl restart ncpa

Step 8: Troubleshooting Tips

Check service status:

sudo systemctl status ncpa
journalctl -u ncpa

Test connectivity:

nc -zv <AlmaLinux-IP> 5693

View logs:

cat /usr/local/ncpa/var/log/ncpa.log

Ensure token/IP match in Nagios XI wizard

Conclusion

With NCPA installed and configured on AlmaLinux 9, you’re now monitoring key system metrics in real time from Nagios XI. For advanced setups, explore encrypted transport or plugin-based checks via the NCPA API.

For help, visit: