This step-by-step guide will walk you through installing and configuring NCPA on RHEL 7, ensuring seamless monitoring and proactive issue resolution with Nagios XI.

Prerequisites

Before proceeding, ensure you have:

• A RHEL 7 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 7 is using the Nagios repository. To add the repository, run:

sudo rpm -Uvh https://repo.nagios.com/nagios/7/nagios-repo-7-2.el7.noarch.rpm
sudo yum update -y

sudo rpm -Uvh https://repo.nagios.com/nagios/7/nagios-repo-7-2.el7.noarch.rpm
sudo yum update -y

After adding the repository, update your package list to ensure you have access to the latest packages.

Step 2: Install NCPA on RHEL 7

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

sudo yum install ncpa -y

sudo yum install ncpa -y

Verify the installation by checking the package version:

rpm -q ncpa

rpm -q ncpa

Expected output: ncpa-<version>.el7.x86_64 (e.g., ncpa-3.1.1-1.el7.x86_64).

Step 3: Configure NCPA

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

1. Open the configuration file:

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

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

2. Locate the line:

 community_string = mytoken

 community_string = mytoken

3. Replace mytoken with a strong, unique token (e.g., K9pL3mX7vR2tQ8nJ) to enhance security.

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

Step 4: Enable and Start the NCPA Service

Ensure NCPA runs automatically at boot and starts immediately by executing:

sudo systemctl enable ncpa
sudo systemctl start ncpa

sudo systemctl enable ncpa
sudo systemctl start ncpa

Check the service status to confirm it is active:

sudo systemctl status ncpa

sudo systemctl status ncpa

You should see Active: active (running) in the output.

Step 5: Configure Firewall Rules

If firewall 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 the firewall rules with:

sudo firewall-cmd --list-ports

sudo firewall-cmd --list-ports

Step 6: Test NCPA Installation

After configuring the firewall, confirm that NCPA is accessible:

1. Open a web browser and navigate to:

https://<NCPA_IP_Address>:5693/

https://<NCPA_IP_Address>:5693/

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

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

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

1. Log in to Nagios XI.

2. Navigate to Configure > Run a Configuration Wizard.

3. Search for and select NCPA.

4. Enter the RHEL 7 server’s IP address and the API token you set in the NCPA configuration.

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

6. Apply the configuration and verify that Nagios XI is collecting data from your RHEL 7 host.

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 for proper IP and token settings.

Incorrect API Token Error

• Confirm the correct API token is set in /usr/local/ncpa/etc/ncpa.cfg.
• Restart the NCPA service after making changes.

Conclusion

You have successfully installed and configured NCPA on RHEL 7 for monitoring with Nagios XI. This setup enables efficient tracking of system performance metrics and ensures proactive issue resolution through real-time monitoring. For further assistance, refer to the Nagios Support Forum or the Nagios Knowledgebase.

In this guide, you’ll learn how to set up and configure SNMP on RHEL 7, allowing Nagios XI to track key system metrics effortlessly using its built-in SNMP monitoring capabilities.

Prerequisites

Ensure you have the following before starting:

• A RHEL 7 system with root or sudo privileges
• Nagios XI is installed and accessible
• SNMP Wizard enabled in Nagios XI
• Network access between the RHEL 7 server and Nagios XI

Step 1: Install SNMP on RHEL 7

1. To install SNMP and the required libraries, run:

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

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

2. After installation, verify the installed version:

snmpd -v

snmpd -v

Step 2: Configure SNMP Access

SNMP v2c Configuration

Backup config:

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

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

Create a new config:

echo 'rocommunity Str0ngC0mmunity 10.25.5.12' > /etc/snmp/snmpd.conf

echo 'rocommunity Str0ngC0mmunity 10.25.5.12' > /etc/snmp/snmpd.conf

Replace Str0ngC0mmunity and 10.25.5.12 accordingly.

Restart SNMP:

systemctl restart snmpd.service

systemctl restart snmpd.service

SNMP v3 Configuration

Stop service:

systemctl stop snmpd.service

systemctl stop snmpd.service

Create user:

sudo net-snmp-create-v3-user -ro -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy nagios

sudo net-snmp-create-v3-user -ro -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy nagios

Start service:

sudo systemctl restart snmpd.service

sudo systemctl restart snmpd.service

Step 3: Configure Firewall Rules

Allow SNMP traffic:

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

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

Verify:

firewall-cmd --list-ports

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

From the Nagios XI server:

SNMP v2c:

snmpwalk -v2c -c Str0ngC0mmunity 10.25.5.12

snmpwalk -v2c -c Str0ngC0mmunity 10.25.5.12

SNMP v3:

snmpwalk -v3 -u nagios -l authPriv -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy 10.25.5.12

snmpwalk -v3 -u nagios -l authPriv -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy 10.25.5.12

Expected output:

iso.3.6.1.2.1.1.1.0 = STRING: "Linux rhel7 3.10.0-1160.el7.x86_64"

iso.3.6.1.2.1.1.1.0 = STRING: "Linux rhel7 3.10.0-1160.el7.x86_64"

If no data is returned, check the firewall and SNMP config.

Step 6: Add RHEL 7 Host to Nagios XI

1. Log in to Nagios XI.

2. Navigate to Configure > Run a configuring wizard.

3. Select the Linux SNMP wizard.

4. Enter the RHEL 7 server’s IP address and SNMP credentials.

5. Select metrics to monitor (CPU, memory, disk, network traffic, etc.).

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

Common Issues & Fixes

SNMP Service is Not Running

1. Check logs for errors:

journalctl -u snmpd --no-pager | tail -20

journalctl -u snmpd --no-pager | tail -20

2. Restart SNMP if necessary:

systemctl restart snmpd.service

systemctl restart snmpd.service

Host Appears “Down” in Nagios XI

1. Confirm SNMP is running:

systemctl status snmpd

systemctl status snmpd

2. Check if port 161 is open:

firewall-cmd --list-ports

firewall-cmd --list-ports

3. Verify SNMP credentials in Nagios XI.

Conclusion

You’ve now configured SNMP on RHEL 7 for agentless monitoring in Nagios XI. This setup improves visibility into your server’s health and performance.

For additional resources:

• Nagios Knowledgebase
• Nagios Support Forum
• Nagios Library