How to Monitor RHEL 8 Using NCPA with Nagios XI

Efficient server monitoring is crucial for maintaining optimal system performance and preventing potential issues before they escalate. The Nagios Cross-Platform Agent (NCPA) is a lightweight, agent-based tool that simplifies real-time monitoring for Linux systems like Red Hat Enterprise Linux (RHEL) 8. 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 will walk you through the installation and configuration process of NCPA on RHEL 8, enabling you to monitor your system comprehensively through Nagios XI.

Prerequisites

Before proceeding, ensure you have:

• A RHEL 8 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

The recommended method for installing NCPA on RHEL 8 is using the Nagios repository. To add the repository, run:

sudo rpm -Uvh https://repo.nagios.com/nagios/8/nagios-repo-8-2.el8.noarch.rpm
yum update

sudo rpm -Uvh https://repo.nagios.com/nagios/8/nagios-repo-8-2.el8.noarch.rpm
yum update

After adding the repository, update your package list:

sudo dnf clean all
sudo dnf update -y

sudo dnf clean all
sudo dnf update -y

Step 2: Install NCPA on RHEL 8

Once the repository is configured, install the NCPA agent using:

sudo dnf install ncpa -y

sudo dnf install ncpa -y

Verify the installation:

rpm -q ncpa

rpm -q ncpa

Expected output: ncpa-<version>.el8.x86_64 (e.g., ncpa-3.1.1-1.el8.x86_64).

Step 3: Configure NCPA

After installation, configure NCPA by editing its configuration file to set your API token:

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

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

Find the line:

community_string = mytoken

community_string = mytoken

Replace mytoken with a strong, unique token (e.g., K9pL3mX7vR2tQ8nJ), avoiding predictable values for security.

Save the file (CTRL + X, then Y, and Enter).

Step 4: Enable and Start the NCPA Service

To ensure NCPA runs automatically at boot and starts immediately, run:

sudo systemctl enable ncpa
sudo systemctl start ncpa

sudo systemctl enable ncpa
sudo systemctl start ncpa

Check if the service is running:

sudo systemctl status ncpa

sudo systemctl status ncpa

Confirm Active: active (running) appears in the output.

Step 5: Configure Firewall Rules

If firewalld is active (check with sudo systemctl status firewalld), allow NCPA traffic 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

Confirm firewall rules:

sudo firewall-cmd --list-ports

sudo firewall-cmd --list-ports

Step 6: Test NCPA Installation

After configuring the firewall, confirm that NCPA is accessible by navigating to:

https://<NCPA_IP_Address>:5693/

https://<NCPA_IP_Address>:5693/

Since NCPA uses a self-signed certificate, your browser may display a warning. Click Advanced > Proceed to continue.

You should see the NCPA login page. Enter the API token you configured earlier and click Log In.

Step 7: Add RHEL 8 Host to Nagios XI Using NCPA Wizard

1. Log in to Nagios XI.

2. Navigate to Configure > Configuring wizard.

3. Search for and select NCPA.

4. Enter the RHEL 8 server’s IP address and API token.

5. Click Next, select the system metrics to monitor (CPU, memory, disk, network traffic, etc.).

6. Apply the configuration and verify that Nagios XI is collecting data.

Common Issues & Fixes

NCPA Service is Not Running

Check logs for errors:

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

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

Restart NCPA if necessary:

sudo systemctl restart ncpa

sudo systemctl restart ncpa

Host Appears “Down” in Nagios XI

• Check firewall rules:

sudo firewall-cmd --list-ports

sudo firewall-cmd --list-ports

• Ensure NCPA is running:

sudo systemctl status ncpa

sudo systemctl status ncpa

• Verify Nagios XI configuration

Incorrect API Token Error

• Confirm the correct API token is set in ncpa.cfg
• Restart the NCPA service after changes

Conclusion

You have successfully installed and configured NCPA on RHEL 8 for monitoring with Nagios XI. This setup allows efficient tracking of system performance metrics and ensures proactive issue resolution.

For further assistance, refer to the Nagios Support Forum or the Nagios Knowledgebase.