checkmk-agent

Official Check_MK monitoring agent for OpenWrt-based systems.

Description

This package provides the official Check_MK agent binary along with service management for NethSecurity. The agent is exposed via TCP port 6556 using socat, enabling remote monitoring server connections.

For NethSecurity-specific plugins and utilities, install the complementary ns-checkmk-utils package.

Features

Official Check_MK agent binary from upstream project
Procd-managed service with automatic restart on failure
TCP listener on port 6556 via socat
Starts automatically on boot (START=98)
Low dependency footprint

Dependencies

socat: Used to expose the agent via TCP socket and manage keepalive connections

Installation

# Install the package
opkg install checkmk-agent

# Start the service
/etc/init.d/check_mk_agent start

# Enable on boot
/etc/init.d/check_mk_agent enable

Service Management

The agent is managed by procd and monitored for failures.

# Start/stop the service
/etc/init.d/check_mk_agent start
/etc/init.d/check_mk_agent stop

# Restart the service
/etc/init.d/check_mk_agent restart

# Enable/disable on boot
/etc/init.d/check_mk_agent enable
/etc/init.d/check_mk_agent disable

# View service status
/etc/init.d/check_mk_agent status

Testing

Test the agent locally or remotely:

# Run agent directly to verify it works
/usr/sbin/check_mk_agent

# Test via TCP from the monitoring server
echo "" | nc <firewall-ip> 6556

Firewall Rules

Port 6656 is open only from LAN by default. To allow monitoring server access, add a firewall rule to permit incoming connections on TCP port 6556 from the monitoring server’s IP address or subnet. Ensure your Check_MK monitoring server can reach the firewall on TCP port 6556:

# Allow connections from monitoring server (example)
uci add firewall rule
uci set firewall.@rule[-1].name='Allow Check_MK'
uci set firewall.@rule[-1].src='wan'
uci set firewall.@rule[-1].proto='tcp'
uci set firewall.@rule[-1].dest_port='6556'
uci set firewall.@rule[-1].target='ACCEPT'
uci commit firewall

Extending with Plugins

To add NethSecurity-specific plugins and utilities, install the ns-checkmk-utils package:

opkg install ns-checkmk-utils

Plugins are stored in /usr/lib/check_mk_agent/local and are automatically executed by the agent.

Troubleshooting

Agent not responding on port 6556:

Verify the service is running: /etc/init.d/check_mk_agent status
Check firewall rules allow inbound traffic on port 6556
Test locally: /usr/sbin/check_mk_agent