Getting Started

Once configured, logs typically found in /var/log/messages will be forwarded to Nagios Log Server R2, enabling centralized monitoring and alerting.

Automatic Setup Using a Script

The simplest way to configure log forwarding is by using the provided setup script. This method requires rsyslog to be installed on your RHEL 9 system.

Steps to Run the Script:

1. Ensure Rsyslog is Installed:

sudo dnf install rsyslog -y
sudo systemctl enable --now rsyslog

sudo dnf install rsyslog -y
sudo systemctl enable --now rsyslog

2. Download the script from the Nagios Log Server R2:

curl -sS -O http://192.168.1.49/nagioslogserver/scripts/setup-linux.sh

curl -sS -O http://192.168.1.49/nagioslogserver/scripts/setup-linux.sh

3. Execute the Script to Configure Rsyslog:

sudo bash setup-linux.sh -s 192.168.1.49 -p 5544

sudo bash setup-linux.sh -s 192.168.1.49 -p 5544

• Replace 192.168.1.49 with the IP address of your Nagios Log Server R2.
• The -p 5544 option specifies the port for log transmission.

Manual Setup Using Rsyslog Configuration

For greater control over configurations, follow these manual setup steps:

1. Edit Rsyslog Configuration:

sudo nano /etc/rsyslog.d/99-nagios.conf

sudo nano /etc/rsyslog.d/99-nagios.conf

2. Add the Following Configuration:

*.* @@192.168.1.49:5544

*.* @@192.168.1.49:5544

• Replace 192.168.1.49 with the IP address of your Nagios Log Server R2.
• The @@ symbol indicates TCP transmission; use @ for UDP if required.

3. Restart Rsyslog to Apply Changes:

sudo systemctl restart rsyslog

sudo systemctl restart rsyslog

4. Verify Rsyslog Status:

sudo systemctl status rsyslog

sudo systemctl status rsyslog

Receiving Logs in Log Server

On your Log Server’s GUI, click Add Log Source.

Click Linux.

Type in your machine’s IP address to see if you are receiving logs. If it’s working, the interface will confirm that logs are being received.

Conclusion

Whether using the automatic script or manual configuration, forwarding logs from RHEL 9 to Nagios Log Server R2 ensures centralized log management for improved monitoring and alerting. Choose the method that best fits your deployment requirements.

Prerequisites

Before proceeding, make sure you have:

• A RHEL 9 system with root or sudo privileges.
• Nagios XI is 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 9 is by using the Nagios repository. To add the repository, run:

sudo rpm -Uvh https://repo.nagios.com/nagios/9/nagios-repo-9-2.el9.noarch.rpm
sudo dnf update

sudo rpm -Uvh https://repo.nagios.com/nagios/9/nagios-repo-9-2.el9.noarch.rpm
sudo dnf 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 9

Once the repository is set up, 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-.el9.x86_64 (e.g., ncpa-3.1.1-1.el9.x86_64)

ncpa-.el9.x86_64 (e.g., ncpa-3.1.1-1.el9.x86_64)

Step 3: Configure NCPA

After installation, configure NCPA by editing the 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), ensuring it is not predictable for security reasons.

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 that the output shows Active: active (running).

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 9 Host to Nagios XI Using NCPA Wizard

Log in to Nagios XI.

Navigate to Configure > Configuring Wizard.

Search for and select NCPA.

Enter the RHEL 9 server’s IP address and the API token.

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

Apply the configuration and verify that Nagios XI is collecting data from your RHEL 9 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 the Nagios XI configuration.

Incorrect API Token Error

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

Conclusion

You have successfully installed and configured NCPA on RHEL 9 for monitoring with Nagios XI. This setup enables you to efficiently track system performance metrics and ensure proactive issue resolution.

This guide will walk you through the process of installing and configuring SNMP on RHEL 9, allowing you to integrate it easily with Nagios XI for efficient server monitoring.

Prerequisites

Before you begin, ensure the following:

• A RHEL 9 system with root or sudo privileges.
• Nagios XI installed and accessible, with the SNMP Wizard enabled.
• A stable internet connection for downloading packages.

Step 1: Install SNMP on RHEL 9

To install SNMP and the required libraries, run the following command:

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

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

After installation, verify that SNMP has been successfully installed:

snmpd -v 

snmpd -v 

Step 2: Configure SNMP Access

SNMP v2c Configuration

1. To configure SNMP v2c, create a backup of the existing configuration:

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

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

2. Now, edit the SNMP configuration file:

sudo nano /etc/snmp/snmpd.conf

sudo nano /etc/snmp/snmpd.conf

3. Find and modify the following line to define the community string and allow access from your Nagios XI server (replace Str0ngC0mmunity with your desired community string and 10.25.5.12 with your Nagios XI server’s IP address):

rocommunity Str0ngC0mmunity 10.25.5.12

rocommunity Str0ngC0mmunity 10.25.5.12

4. Save the file and restart the SNMP service:

sudo systemctl restart snmpd.service

sudo systemctl restart snmpd.service

SNMP v3 Configuration (More Secure)

1. Stop the SNMP service temporarily:

sudo systemctl stop snmpd.service

sudo systemctl stop snmpd.service

2. To configure SNMP v3, create an SNMP user with authentication and encryption:

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

• -a SHA → Specifies SHA for authentication (MD5 is also supported but less secure).
• -x AES → Enables AES encryption (DES is another option but less secure).

3. Restart the SNMP service:

sudo systemctl restart snmpd.service

sudo systemctl restart snmpd.service

Step 3: Configure Firewall Rules

1. If firewall is active (check with sudo systemctl status firewalld), allow SNMP traffic on UDP port 161:

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

2. Confirm firewall rules:

sudo firewall-cmd --list-ports

sudo firewall-cmd --list-ports

Step 4: Enable SNMP Service on Boot

To ensure SNMP starts automatically at boot, run:

sudo systemctl enable snmpd.service

sudo systemctl enable snmpd.service

Step 5: Test SNMP Communication

To test if SNMP is responding correctly, run the following commands from your Nagios XI server.

For SNMP v2c:

snmpwalk -v2c -c Str0ngC0mmunity 10.25.5.12

snmpwalk -v2c -c Str0ngC0mmunity 10.25.5.12

For 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 (Example)

iso.3.6.1.2.1.1.1.0 = STRING: "Linux myserver 4.18.0-305.19.1.el8.x86_64"
iso.3.6.1.2.1.1.3.0 = Timeticks: (100032) 0:16:40.32

iso.3.6.1.2.1.1.1.0 = STRING: "Linux myserver 4.18.0-305.19.1.el8.x86_64"
iso.3.6.1.2.1.1.3.0 = Timeticks: (100032) 0:16:40.32

If the command does not return data, review SNMP configuration and firewall settings.

Step 6: Add RHEL 8 Host to Nagios XI Using SNMP Wizard

Log in to Nagios XI.

Navigate to Configure > Run a Configuration Wizard.

Search for and select the Linux SNMP Wizard.

Enter the IP address of your RHEL 9 server and the SNMP credentials.

Click Next, then choose the system metrics you wish to monitor (CPU, memory, disk usage, network traffic, etc.).

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

Common Issues & Fixes

SNMP Service is Not Running

Check logs for errors:

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

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

Restart SNMP if necessary:

sudo systemctl restart snmpd.service

sudo systemctl restart snmpd.service

Host Appears “Down” in Nagios XI

• Check firewall rules:

sudo firewall-cmd --list-ports

sudo firewall-cmd --list-ports

• Ensure SNMP is running:

sudo systemctl status snmpd

sudo systemctl status snmpd

• Verify Nagios XI configuration

Incorrect SNMP Credentials Error

Confirm that the correct community string (for SNMP v2c) or authentication details (for SNMP v3) are used.

Restart the SNMP service after making changes:

sudo systemctl restart snmpd.service

sudo systemctl restart snmpd.service

Conclusion

You’ve successfully configured SNMP on RHEL 9 for agentless monitoring with Nagios XI, providing real-time insights into system performance. For advanced setups, explore custom SNMP OIDs or additional Nagios XI plugins. For support, visit the Nagios Support Forum or the Nagios Knowledgebase.