NixOS – Nagios Library

Monitoring NixOS with SNMP in Nagios XI: A Step-by-Step Guide

Ayub Huruse — Mon, 31 Mar 2025 21:01:48 +0000

NixOS is a distinctive Linux distribution focused on reproducibility and declarative configuration, utilizing the Nix package manager. Unlike traditional distributions, NixOS doesn’t follow conventional package management workflows, but it supports SNMP (Simple Network Management Protocol) for agentless monitoring. This guide details installing SNMP on NixOS, configuring SNMP v2c or v3, and integrating it with Nagios XI for real-time monitoring of system metrics like CPU, memory, disk, and network usage as of March 2025.

Prerequisites

Ensure:

A NixOS system (updated with sudo nix-channel --update && sudo nixos-rebuild switch) with sudo or root access.
A running Nagios XI instance (latest version recommended).
Network connectivity between NixOS and Nagios XI (UDP port 161 open).
Access to edit /etc/nixos/configuration.nix.

Step 1: Install SNMP Packages

Option 1: Imperative Installation (For Testing)

nix-env -iA nixos.net-snmp

nix-env -iA nixos.net-snmp

Verify:

snmpd --version

snmpd --version

Option 2: Declarative Installation (Recommended)

Add to /etc/nixos/configuration.nix:

environment.systemPackages = with pkgs; [ net-snmp ];

environment.systemPackages = with pkgs; [ net-snmp ];

Apply changes:

sudo nixos-rebuild switch

sudo nixos-rebuild switch

Verify:

/run/current-system/sw/bin/snmpd --version

/run/current-system/sw/bin/snmpd --version

Step 2: Configure SNMP Access

Option 1: SNMP v2c

sudo mkdir -p /etc/snmp
sudo cp /etc/snmp/snmpd.conf /etc/snmp/snmpd.bak 2>/dev/null || true
echo "rocommunity Str0ngC0mmunity <Nagios-XI-IP>" | sudo tee /etc/snmp/snmpd.conf

sudo mkdir -p /etc/snmp
sudo cp /etc/snmp/snmpd.conf /etc/snmp/snmpd.bak 2>/dev/null || true
echo "rocommunity Str0ngC0mmunity " | sudo tee /etc/snmp/snmpd.conf

Replace with your Nagios XI server IP (e.g., 10.25.5.12).

Option 2: SNMP v3 (Secure)

sudo systemctl stop snmpd.service
sudo net-snmp-create-v3-user -ro -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy nagios
sudo mkdir -p /etc/snmp
echo "rouser nagios authPriv" | sudo tee /etc/snmp/snmpd.conf

sudo systemctl stop snmpd.service
sudo net-snmp-create-v3-user -ro -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy nagios
sudo mkdir -p /etc/snmp
echo "rouser nagios authPriv" | sudo tee /etc/snmp/snmpd.conf

Step 3: Configure Firewall

Declarative Method (Recommended)

Add to /etc/nixos/configuration.nix:

networking.firewall.allowedUDPPorts = [ 161 ];

networking.firewall.allowedUDPPorts = [ 161 ];

Apply changes:

sudo nixos-rebuild switch

sudo nixos-rebuild switch

Verify:

sudo iptables -L -n | grep 161

sudo iptables -L -n | grep 161

Imperative Method (Temporary)

sudo iptables -I INPUT -p udp --dport 161 -j ACCEPT
sudo mkdir -p /etc/iptables
sudo iptables-save > /etc/iptables/rules.v4

sudo iptables -I INPUT -p udp --dport 161 -j ACCEPT
sudo mkdir -p /etc/iptables
sudo iptables-save > /etc/iptables/rules.v4

Step 4: Enable SNMP Daemon on Boot

Add to /etc/nixos/configuration.nix:

systemd.services.snmpd = {
  description = "SNMP Daemon";
  after = [ "network.target" ];
  wantedBy = [ "multi-user.target" ];
  serviceConfig = {
    ExecStart = "${pkgs.net-snmp}/bin/snmpd -c /etc/snmp/snmpd.conf";
    Restart = "on-failure";
  };
};

systemd.services.snmpd = {
  description = "SNMP Daemon";
  after = [ "network.target" ];
  wantedBy = [ "multi-user.target" ];
  serviceConfig = {
    ExecStart = "${pkgs.net-snmp}/bin/snmpd -c /etc/snmp/snmpd.conf";
    Restart = "on-failure";
  };
};

Apply changes:

sudo nixos-rebuild switch

sudo nixos-rebuild switch

Verify:

sudo systemctl status snmpd.service

sudo systemctl status snmpd.service

Step 5: Test SNMP Communication

Install SNMP tools on Nagios XI (if needed):

sudo dnf install net-snmp-utils -y

sudo dnf install net-snmp-utils -y

SNMP v2c

snmpwalk -v2c -c Str0ngC0mmunity <NixOS-IP>

snmpwalk -v2c -c Str0ngC0mmunity

SNMP v3

snmpwalk -v3 -u nagios -l authPriv -a SHA -A Str0ng@uth3ntic@ti0n -x AES -X Str0ngPriv@cy <NixOS-IP>

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

Expected output:

iso.3.6.1.2.1.1.1.0 = STRING: "Linux nixos-<hostname> <version> x86_64"

iso.3.6.1.2.1.1.1.0 = STRING: "Linux nixos-  x86_64"

Step 6: Add Host to Nagios XI Using SNMP Wizard

Log into Nagios XI
Navigate to Configure > Configuration Wizards
Select Linux SNMP
Configure Host:
- IP: 192.168.0.31
- SNMP Version: v2c or v3
- v2c Community: Str0ngC0mmunity
- v3 Username: nagios, Auth Protocol: SHA, Auth Password: Str0ng@uth3ntic@ti0n, Privacy Protocol: AES, Privacy Password: Str0ngPriv@cy
Click Next, select metrics (CPU, memory, disk, etc.)
Click Finish and apply
Verify monitoring in Monitoring > Hosts

Troubleshooting

SNMP Not Responding

sudo systemctl status snmpd
ps aux | grep snmpd
sudo systemctl restart snmpd

sudo systemctl status snmpd
ps aux | grep snmpd
sudo systemctl restart snmpd

Firewall Issue

sudo iptables -L -n
sudo nc -zu <NixOS-IP> 161

sudo iptables -L -n
sudo nc -zu  161

Log SNMP Output

sudo /run/current-system/sw/bin/snmpd -f -Lo -c /etc/snmp/snmpd.conf

sudo /run/current-system/sw/bin/snmpd -f -Lo -c /etc/snmp/snmpd.conf

Conclusion

You’ve configured SNMP on NixOS and integrated it with Nagios XI for agentless, real-time monitoring as of March 28, 2025. NixOS’s declarative nature requires explicit setup for SNMP, but this approach ensures reliability. For long-term stability, maintain all configurations (packages, firewall, services) in /etc/nixos/configuration.nix. Explore further customization in the Nagios SNMP Guide, Net-SNMP Documentation, or NixOS Manual.

Comprehensive Guide to Monitoring NixOS with NCPA in Nagios XI

Ayub Huruse — Fri, 28 Mar 2025 16:18:13 +0000

NixOS is a distinctive Linux distribution known for its declarative configuration, atomic upgrades, and reproducible builds, leveraging the Nix package manager. Unlike traditional distributions, NixOS doesn’t natively support RPM-based packages like the Nagios Cross-Platform Agent (NCPA) from standard repositories. However, NCPA can be manually installed to monitor system metrics such as CPU usage, memory, disk usage, and processes, integrating seamlessly with Nagios XI for real-time oversight. This guide details the manual installation and configuration of NCPA (latest version as of March 2025) on NixOS and its integration with Nagios XI, tailored to NixOS’s unique environment.

Prerequisites

Ensure:

A NixOS system (updated with sudo nix-channel --update && sudo nixos-rebuild switch) with sudo or root access.
A running Nagios XI instance (latest version recommended).
Network connectivity between NixOS and Nagios XI (port 5693/TCP open).
Basic utilities installed: curl, rpm2cpio, cpio, and python3 (not all are default in NixOS).

Step 1: Prepare the Environment

NixOS requires specific tools to extract the NCPA RPM, which aren’t included by default:

1. Install Required Tools:

sudo nix-env -iA nixos.curl nixos.rpm-tools nixos.cpio

sudo nix-env -iA nixos.curl nixos.rpm-tools nixos.cpio

2. Verify Installation:

curl --version rpm2cpio --version cpio --version

curl --version rpm2cpio --version cpio --version

Declarative Alternative:

environment.systemPackages = with pkgs; [ curl rpm-tools cpio ];

environment.systemPackages = with pkgs; [ curl rpm-tools cpio ];

Then run:

sudo nixos-rebuild switch

sudo nixos-rebuild switch

Step 2: Download and Extract NCP

1. Create a Working Directory:

mkdir -p ~/ncpa && cd ~/ncpa

mkdir -p ~/ncpa && cd ~/ncpa

2. Download the Latest NCPA RPM:

curl -O https://assets.nagios.com/downloads/ncpa3/ncpa-latest-1.x86_64.rpm

curl -O https://assets.nagios.com/downloads/ncpa3/ncpa-latest-1.x86_64.rpm

3. Extract the RPM:

rpm2cpio ncpa-latest-1.x86_64.rpm | cpio -idmv

rpm2cpio ncpa-latest-1.x86_64.rpm | cpio -idmv

Step 3: Install NCPA Files Manually

sudo cp -r ./usr/* /usr/
sudo cp -r ./etc/* /etc/
sudo cp -r ./var/* /var/

sudo cp -r ./usr/* /usr/
sudo cp -r ./etc/* /etc/
sudo cp -r ./var/* /var/

Step 4: Configure NCPA

1. Edit the Config File:

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

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

2. Update the token:

Locate:

community_string = mytoken

community_string = mytoken

Replace with:

community_string = Str0ngT0k3n2025

community_string = Str0ngT0k3n2025

Save and exit (Ctrl+O, Enter, Ctrl+X in nano).

Step 5: Start NCPA

NixOS uses systemd but prefers declarative service management. Start NCPA manually or create a custom systemd unit:

Option 1: Manual Start

sudo /usr/local/ncpa/ncpa_listener &

sudo /usr/local/ncpa/ncpa_listener &

Runs in the background; use fg to bring it forward or kill to stop it.

Option 2: Create a Systemd Unit

1. Create a Service File:

sudo nano /etc/systemd/system/ncpa.service

sudo nano /etc/systemd/system/ncpa.service

Add the Following:

[Unit]
Description=NCPA Listener Service
After=network.target

[Service]
Type=simple
ExecStart=/usr/local/ncpa/ncpa_listener
Restart=on-failure

[Install]
WantedBy=multi-user.target

[Unit]
Description=NCPA Listener Service
After=network.target

[Service]
Type=simple
ExecStart=/usr/local/ncpa/ncpa_listener
Restart=on-failure

[Install]
WantedBy=multi-user.target

Enable and Start:

sudo systemctl daemon-reload
sudo systemctl enable ncpa
sudo systemctl start ncpa

sudo systemctl daemon-reload
sudo systemctl enable ncpa
sudo systemctl start ncpa

Declarative Alternative: Add to /etc/nixos/configuration.nix:

systemd.services.ncpa = {
  description = "NCPA Listener Service";
  after = [ "network.target" ];
  wantedBy = [ "multi-user.target" ];
  serviceConfig = {
    ExecStart = "/usr/local/ncpa/ncpa_listener";
    Restart = "on-failure";
  };
};

systemd.services.ncpa = {
  description = "NCPA Listener Service";
  after = [ "network.target" ];
  wantedBy = [ "multi-user.target" ];
  serviceConfig = {
    ExecStart = "/usr/local/ncpa/ncpa_listener";
    Restart = "on-failure";
  };
};

Then run:

sudo nixos-rebuild switch

sudo nixos-rebuild switch

Step 6: Configure Firewall

sudo iptables -I INPUT -p tcp --dport 5693 -j ACCEPT
sudo mkdir -p /etc/iptables
sudo iptables-save > /etc/iptables/rules.v4

sudo iptables -I INPUT -p tcp --dport 5693 -j ACCEPT
sudo mkdir -p /etc/iptables
sudo iptables-save > /etc/iptables/rules.v4

verify:

sudo iptables -L -n | grep 5693

sudo iptables -L -n | grep 5693

Declarative Firewall: Add to /etc/nixos/configuration.nix:

networking.firewall.allowedTCPPorts = [ 5693 ];

networking.firewall.allowedTCPPorts = [ 5693 ];

Then run:

sudo nixos-rebuild switch

sudo nixos-rebuild switch

Step 7: Test NCPA Access

1. Access the NCPA Web Interface:

Open a browser:

https://<NixOS-IP>:5693/

https://:5693/

2. Accept Certificate:

Accept the self-signed certificate warning.

3. Log In:

Verify metrics like CPU, memory, and disk usage are displayed.
Use the token (e.g., Str0ngT0k3n2025) to access the dashboard.

Step 8: Add NixOS to Nagios XI

1. Log into Nagios XI:

Access the web interface.

2. Run the NCPA Wizard:

Navigate to Configure > Configuration Wizards.
Select NCPA.

NCPA

3. Configure the Host:

IP Address: Enter the NixOS IP (e.g., 192.168.0.31).
Port: Use 5693.
Token: Input Str0ngT0k3n2025.
Metrics: Select CPU Usage, Memory Usage, Disk Usage, Processes, etc.
Set thresholds (e.g., CPU warning at 80%, critical at 90%).

NixOS Credentials

4. Apply Configuration:

Click Finish and apply changes.

5. Verify Monitoring:

Go to Monitoring > Hosts, locate your NixOS host, and check service statuses.

Troubleshooting

#Check process:
ps aux | grep ncpa_listener

#Check systemd (if used):
sudo systemctl status ncpa

#Review logs:
cat /usr/local/ncpa/var/log/ncpa.log

#Test connectivity:
nc -zv <NixOS-IP> 5693

#Check firewall:
iptables -L -n
cat /usr/local/nagiosxi/var/ncpa.log

#Check process:
ps aux | grep ncpa_listener

#Check systemd (if used):
sudo systemctl status ncpa

#Review logs:
cat /usr/local/ncpa/var/log/ncpa.log

#Test connectivity:
nc -zv  5693

#Check firewall:
iptables -L -n
cat /usr/local/nagiosxi/var/ncpa.log

Conclusion

You’ve manually installed NCPA on NixOS and integrated it with Nagios XI as of March 28, 2025. While NixOS’s declarative nature doesn’t align with NCPA’s standard RPM packaging, this workaround enables robust monitoring. For a more Nix-native approach, consider packaging NCPA as a Nix derivation or persisting files in /opt and managing services/firewall declaratively in /etc/nixos/configuration.nix. Explore further customization like passive checks via NRDP in the Nagios NCPA , Nagios Knowledgebase, or NixOS Documentation.