This guide provides a step-by-step walkthrough on configuring SNMP on Rocky Linux 9, a reliable RHEL-compatible distribution, and seamlessly integrating it with Nagios XI for real-time monitoring.

Prerequisites

Before you begin, make sure you have:

• A Rocky Linux 9 system with root or sudo privileges
• A working Nagios XI server with SNMP Wizard enabled
• Network connectivity between the server and Nagios XI
• Port 161/UDP open in the Rocky Linux firewall

Step 1: Install SNMP and Utilities

sudo dnf install net-snmp net-snmp-utils -y

sudo dnf install net-snmp net-snmp-utils -y

Verify installation:

snmpd -v

snmpd -v

Step 2: Configure SNMP Access

SNMP v2c Configuration

1. Backup the default config:

sudo cp /etc/snmp/snmpd.conf /etc/snmp/snmpd.conf.bak

sudo cp /etc/snmp/snmpd.conf /etc/snmp/snmpd.conf.bak

2. Configure access for Nagios XI:

echo "rocommunity Str0ngC0mmunity <Nagios-XI-IP>" | sudo tee /etc/snmp/snmpd.conf

echo "rocommunity Str0ngC0mmunity <Nagios-XI-IP>" | sudo tee /etc/snmp/snmpd.conf

3. Restart SNMP:

sudo systemctl restart snmpd.service

sudo systemctl restart snmpd.service

SNMP v3 Configuration (More Secure)

1. Stop SNMP service:

sudo systemctl stop snmpd.service

sudo systemctl stop snmpd.service

2. Clear old config and create user:

sudo sh -c "echo '' > /etc/snmp/snmpd.conf"
sudo net-snmp-create-v3-user -ro -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy nagios

sudo sh -c "echo '' > /etc/snmp/snmpd.conf"
sudo net-snmp-create-v3-user -ro -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy nagios

3. Start SNMP:

sudo systemctl start snmpd.service

sudo systemctl start snmpd.service

Step 3: Configure the Firewall

sudo firewall-cmd --zone=public --add-port=161/udp --permanent
sudo firewall-cmd --reload

sudo firewall-cmd --zone=public --add-port=161/udp --permanent
sudo firewall-cmd --reload

Check allowed ports:

sudo firewall-cmd --list-ports

sudo firewall-cmd --list-ports

Step 4: Enable SNMP on Boot

sudo systemctl enable snmpd.service

sudo systemctl enable snmpd.service

Step 5: Test SNMP Communication

Run from the Nagios XI server:

For SNMP v2c:

snmpwalk -v2c -c Str0ngC0mmunity <rocky-linux-ip>

snmpwalk -v2c -c Str0ngC0mmunity <rocky-linux-ip>

For SNMP v3:

snmpwalk -v -u nagios -l authPriv -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy <rocky-linux-ip><br>

snmpwalk -v -u nagios -l authPriv -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy <rocky-linux-ip><br>

Check for responses like:

iso.3.6.1.2.1.1.1.0 = STRING: "Linux rocky9"

iso.3.6.1.2.1.1.1.0 = STRING: "Linux rocky9"

Step 6: Add Rocky Linux 9 to Nagios XI Using the SNMP Wizard

Integrate the Rocky Linux system into Nagios XI:

1. Log into Nagios XI:

• Access the web interface.

2. Run the SNMP Wizard:

• Navigate to Configure > Configuration Wizards.
• Select Linux SNMP.

3. Configure the Host:

• Hostname/IP: Enter the Rocky Linux 9 IP (e.g., 192.168.0.31).
• SNMP Version: Choose v2c or v3.
• For v2c:
  • Community String: Str0ngC0mmunity.
• For v3:
  • Username: nagios.
  • Auth Protocol: SHA.
  • Auth Password: Str0ng@uth3ntic@ti0n.
  • Privacy Protocol: AES.
  • Privacy Password: Str0ngPriv@cy.
• Click Next.

4. Select Metrics:

• Choose CPU, Memory, Disk, Processes, etc.
• Set thresholds (e.g., Disk warning at 80%, critical at 90%).

5. Apply Configuration:

• Click Finish and apply changes.

6. Verify Monitoring:

• Go to Monitoring > Hosts, find your Rocky Linux host, and check service statuses.

Troubleshooting Tips

SNMP Service Not Running

sudo systemctl status snmpd
sudo journalctl -u snmpd --no-pager | tail -20

sudo systemctl status snmpd
sudo journalctl -u snmpd --no-pager | tail -20

Restart service if needed:

sudo systemctl restart snmpd

sudo systemctl restart snmpd

Host Appears Down in Nagios XI

• Ensure SNMP is running
• Verify firewall allows UDP 161
• Double-check SNMP credentials

Conclusion

You’ve now configured Rocky Linux 9 to communicate with Nagios XI via SNMP. Whether using v2c or the more secure v3, SNMP provides essential monitoring capabilities for your Linux infrastructure without the need for additional agents.

For support:

• Nagios Support Forum
• Nagios Knowledgebase

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:

• Nagios Support Forum
• Nagios Knowledgebase