Prerequisites

Ensure you have the following:

• An AlmaLinux 9 server with root or sudo access
• A running Nagios Log Server 2024R2 instance
• Network connectivity between the AlmaLinux server and Log Server (default port 5544 open)
• SELinux disabled or properly configured for rsyslog

Step 1: Access Log Source Setup in Nagios Log Server

1. Log into your Nagios Log Server web interface.

2. Click the + button in the left sidebar and the one at the bottom.

Step 2: Run the Auto-Configuration Script on AlmaLinux 9

1. Copy the setup script command shown in the Nagios interface. It looks similar to:

curl -sS -O http://<logserver-ip>/nagioslogserver/scripts/setup-linux.sh
sudo bash setup-linux.sh -s <logserver-ip> -p 5544

curl -sS -O http://<logserver-ip>/nagioslogserver/scripts/setup-linux.sh
sudo bash setup-linux.sh -s <logserver-ip> -p 5544

• Replace <logserver-ip> with the IP or DNS name of your Nagios Log Server.

2. Example Output:

curl -sS -O http://192.168.1.123/nagioslogserver/scripts/setup-linux.sh 
sudo bash setup-linux.sh -s 192.168.0.31 -p 5544

curl -sS -O http://192.168.1.123/nagioslogserver/scripts/setup-linux.sh 
sudo bash setup-linux.sh -s 192.168.0.31 -p 5544

3. Confirm the script output shows successful configuration:

• “Detected rsyslog…”
• “rsyslog configuration check passed.”
• “rsyslog is running with the new configuration.”

Step 3: Verify Logs Are Reaching Nagios Log Server

1. In the Nagios Log Server web UI, enter the AlmaLinux server’s IP under Verify Incoming Logs.

2. Alternatively, go to Dashboards > Nagios Log Server Search and run:

host.ip:<AlmaLinux-IP>

host.ip:<AlmaLinux-IP>

3. To test log transmission, run:

logger This is a test log entry

logger This is a test log entry

4. Verify the entry appears in the Nagios Log Server interface.

Optional: Manual rsyslog Configuration (Advanced)

If you prefer not to use the script, follow these steps:

1. Create a custom rsyslog config file:

sudo nano /etc/rsyslog.d/.conf

sudo nano /etc/rsyslog.d/.conf

2. Add the following content (replace IP and port as needed):

# ### begin forwarding rule ### NAGIOSLOGSERVER
$WorkDirectory /var/lib/rsyslog
$ActionQueueFileName fwdRule1
$ActionQueueMaxDiskSpace 1g
$ActionQueueSaveOnShutdown on
$ActionQueueType LinkedList
$ActionResumeRetryCount -1
*.* @@192.168.1.123:5544
# ### end of the forwarding rule ###

# ### begin forwarding rule ### NAGIOSLOGSERVER
$WorkDirectory /var/lib/rsyslog
$ActionQueueFileName fwdRule1
$ActionQueueMaxDiskSpace 1g
$ActionQueueSaveOnShutdown on
$ActionQueueType LinkedList
$ActionResumeRetryCount -1
*.* @@192.168.1.123:5544
# ### end of the forwarding rule ###

3. Restart rsyslog:

sudo systemctl restart rsyslog

sudo systemctl restart rsyslog

4. Verify logs are received as in Step 3.

Step 4: Adding More Log Sources

Use the + Add Log Source button to configure:

• Network Device
• Application Logs
• Archived logs

Conclusion

You’ve successfully configured AlmaLinux 9 to send logs to Nagios Log Server 2024R2. Whether using the automatic script or manual configuration, this setup allows centralized logging, simplifying monitoring and analysis. For advanced use cases, explore custom filtering, alerting, and integrations in the Nagios Log Server interface.

Resource

• Nagios Log Server Knowledgebase
• Nagios Support Forum
• AlmaLinux Documentation

This guide walks you through the process of installing and configuring SNMP on AlmaLinux 9 and integrating it with Nagios XI for centralized, real-time system visibility.

Prerequisites

Before proceeding, make sure you have:

• AlmaLinux 9 with root or sudo privileges
• A running Nagios XI server with the SNMP wizard enabled
• Network connectivity between AlmaLinux and Nagios XI

Step 1: Install SNMP on AlmaLinux 9

1. Install the SNMP daemon and utilities:

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

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

2. Verify SNMP 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. Edit the configuration file:

sudo nano /etc/snmp/snmpd.conf

sudo nano /etc/snmp/snmpd.conf

3. Add the following line (replace with your Nagios XI server IP):

rocommunity Str0ngC0mmunity 10.25.5.12

rocommunity Str0ngC0mmunity 10.25.5.12

4. Restart SNMP:

sudo systemctl restart snmpd.service

sudo systemctl restart snmpd.service

SNMP v3 Configuration (More Secure)

1. Stop SNMP temporarily:

sudo systemctl stop snmpd.service

sudo systemctl stop snmpd.service

2. Create a secure SNMP v3 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

3. Restart SNMP:

sudo systemctl restart snmpd.service

sudo systemctl restart snmpd.service

Step 3: Configure Firewall Rules

If firewalld is active:

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

Confirm the rule:

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 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:

iso.3.6.1.2.1.1.1.0 = STRING: "Linux almalinux 9 ..."

iso.3.6.1.2.1.1.1.0 = STRING: "Linux almalinux 9 ..."

If no output appears, verify SNMP configuration and firewall.

Step 6: Add AlmaLinux Host to Nagios XI Using SNMP Wizard

1. Log into Nagios XI.

2. Go to Configure > Run a configuring wizard.

3. Select Linux SNMP wizard.

4. Enter AlmaLinux 9 IP and SNMP settings (community string or SNMP v3 credentials).

5. Choose metrics (CPU, memory, disk, processes).

6. Apply configuration and verify monitoring.

Common Issues & Fixes

SNMP Not Running

sudo journalctl -u snmpd --no-pager | tail -20
sudo systemctl restart snmpd.service

sudo journalctl -u snmpd --no-pager | tail -20
sudo systemctl restart snmpd.service

Host Appears “Down” in Nagios XI

sudo firewall-cmd --list-ports
sudo systemctl status snmpd

sudo firewall-cmd --list-ports
sudo systemctl status snmpd

SNMP Credential Errors

• Confirm SNMP version and credentials in both AlmaLinux and Nagios XI
• Restart SNMP after any changes

Conclusion

You’ve successfully configured AlmaLinux 9 for SNMP monitoring in Nagios XI. This setup allows for secure, agentless tracking of system metrics in real-time. For advanced use, explore custom SNMP OIDs or additional Nagios XI plugins.

For support:

• Nagios Support Forum
• Nagios Knowledgebase

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

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

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

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

Edit:

community_string = Str0ngT0k3n2025

community_string = Str0ngT0k3n2025

Save and exit.

Step 3: Start and Enable NCPA

sudo systemctl restart ncpa
sudo systemctl enable ncpa
sudo systemctl status 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

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

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)

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

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

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

3. Restart NCPA:

sudo systemctl restart ncpa

sudo systemctl restart ncpa

Step 8: Troubleshooting Tips

• Check service status:

sudo systemctl status ncpa
journalctl -u ncpa

sudo systemctl status ncpa
journalctl -u ncpa

• Test connectivity:

nc -zv <AlmaLinux-IP> 5693

nc -zv <AlmaLinux-IP> 5693

• View logs:

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

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:

• Nagios Support Forum
• Nagios Library