corrosion-admin-panel/companion-agent

Corrosion Companion Agent

The Companion Agent is a lightweight Go binary that runs on bare metal Rust dedicated servers to provide process management, file operations, and SteamCMD integration for servers not running on managed game server panels (AMP/Pterodactyl).

Features

• NATS Integration: Connects to Corrosion cloud via NATS with token authentication
• Process Management: Start, stop, restart, and monitor game server process
• File Operations: Remote file management (read, write, delete, list)
• SteamCMD Integration: Automatic server updates via SteamCMD
• Self-Update: Download and apply agent updates from the cloud
• Heartbeat Monitoring: Publishes status every 60 seconds
• Graceful Shutdown: Handles SIGTERM/SIGINT for clean shutdowns
• Crash Detection: Monitors server process and reports crashes
• Zero Configuration: Pre-configured binary downloaded from dashboard

Architecture

┌─────────────────────────────────────────────┐
│         Corrosion Cloud (NATS)              │
│   corrosion.{license_id}.cmd.*              │
│   corrosion.{license_id}.files.*            │
│   corrosion.{license_id}.update.steam       │
└──────────────────┬──────────────────────────┘
                   │ (Outbound connection)
                   │
         ┌─────────▼──────────┐
         │  Companion Agent   │
         │  (This binary)     │
         └─────────┬──────────┘
                   │
         ┌─────────▼──────────┐
         │   Rust Dedicated   │
         │   Server Process   │
         └────────────────────┘

Installation

Prerequisites

• Linux server (Ubuntu/Debian recommended) or Windows Server
• SteamCMD installed
• Rust Dedicated Server installed

Quick Start

1. Download the pre-configured binary from your Corrosion dashboard

2. Make executable (Linux only):

   chmod +x corrosion-companion-linux-amd64
   

3. Set environment variables:

   export NATS_URL="nats://nats.corrosionmgmt.com:4222"
   export NATS_TOKEN="your-companion-token-from-dashboard"
   export LICENSE_ID="your-license-uuid"
   export GAME_SERVER_PATH="/home/rustserver/RustDedicated"
   export STEAMCMD_PATH="/usr/games/steamcmd"
   

4. Run the agent:

   ./corrosion-companion-linux-amd64
   

Production Deployment (Linux with systemd)

1. Copy binary to system location:

   sudo cp corrosion-companion-linux-amd64 /usr/local/bin/corrosion-companion
   

2. Create environment file:

   sudo mkdir -p /etc/corrosion-companion
   sudo nano /etc/corrosion-companion/config.env
   

   Add:

   NATS_URL=nats://nats.corrosionmgmt.com:4222
   NATS_TOKEN=your-companion-token-from-dashboard
   LICENSE_ID=your-license-uuid
   GAME_SERVER_PATH=/home/rustserver/RustDedicated
   STEAMCMD_PATH=/usr/games/steamcmd
   GAME_SERVER_ARGS=-batchmode +server.port 28015 +server.identity "myserver"
   HEARTBEAT_INTERVAL=60
   

3. Create systemd service:

   sudo nano /etc/systemd/system/corrosion-companion.service
   

   Add:

   [Unit]
   Description=Corrosion Companion Agent
   After=network.target
   
   [Service]
   Type=simple
   User=rustserver
   Group=rustserver
   EnvironmentFile=/etc/corrosion-companion/config.env
   ExecStart=/usr/local/bin/corrosion-companion
   Restart=always
   RestartSec=10
   StandardOutput=journal
   StandardError=journal
   
   [Install]
   WantedBy=multi-user.target
   

4. Enable and start:

   sudo systemctl daemon-reload
   sudo systemctl enable corrosion-companion
   sudo systemctl start corrosion-companion
   

5. Check status:

   sudo systemctl status corrosion-companion
   sudo journalctl -u corrosion-companion -f
   

Configuration

All configuration is done via environment variables:

Variable	Required	Default	Description
NATS_URL	Yes	-	NATS server URL
NATS_TOKEN	Yes	-	Authentication token from dashboard
LICENSE_ID	Yes	-	Your Corrosion license UUID
GAME_SERVER_PATH	Yes	-	Full path to game server executable
STEAMCMD_PATH	No	/usr/games/steamcmd	Full path to steamcmd
GAME_SERVER_ARGS	No	-batchmode	Arguments to pass to game server
HEARTBEAT_INTERVAL	No	60	Heartbeat interval in seconds
LOG_LEVEL	No	info	Log verbosity (info/debug/warn/error)

NATS Subject Reference

Published by Companion

Subject	Payload	Frequency
corrosion.{license_id}.companion.heartbeat	Status, uptime, disk, CPU	Every 60s
corrosion.{license_id}.files.response	File operation results	On request

Subscribed by Companion

Subject	Purpose
corrosion.{license_id}.cmd.server	Start/stop/restart commands
corrosion.{license_id}.files.get	Read file
corrosion.{license_id}.files.put	Write file
corrosion.{license_id}.files.delete	Delete file
corrosion.{license_id}.files.list	List directory
corrosion.{license_id}.update.steam	Trigger SteamCMD update
corrosion.{license_id}.update.companion	Self-update command

Building from Source

Prerequisites

• Go 1.21 or later
• Make (optional, but recommended)

Build Commands

# Download dependencies
go mod download

# Build for current platform
make build-local

# Build for Linux (amd64)
make build-linux

# Build for Windows (amd64)
make build-windows

# Build for all platforms
make build

# Run tests
make test

# Format code
make fmt

Binaries are output to bin/ directory.

Troubleshooting

Agent won't connect to NATS

• Verify NATS_URL is correct
• Check firewall allows outbound connections to port 4222
• Verify NATS_TOKEN is valid from dashboard
• Check logs: journalctl -u corrosion-companion -n 50

Server won't start

• Verify GAME_SERVER_PATH points to the correct executable
• Check file permissions (agent needs execute permission on server binary)
• Verify GAME_SERVER_ARGS are correct for your server
• Check server logs for startup errors

SteamCMD updates fail

• Verify STEAMCMD_PATH is correct
• Check SteamCMD is installed: steamcmd +quit
• Ensure disk space is available
• Check network connectivity to Steam servers

Self-update fails

• Verify agent has write permission to its own directory
• Check download URL is accessible
• Ensure sufficient disk space
• Restart agent manually after update if automatic restart fails

Security Considerations

• Token Security: Keep NATS_TOKEN secret. It grants full control over your server.
• File Operations: The agent can read/write/delete files. It runs with the permissions of the user running it.
• Process Control: The agent can start/stop the game server process.
• Network: The agent only makes outbound connections (no inbound ports required).
• Updates: Self-updates download from URLs provided by Corrosion cloud (signed URLs).

Support

• Documentation: https://docs.corrosionmgmt.com
• Dashboard: https://panel.corrosionmgmt.com
• Issues: Report via dashboard or contact support

License

Proprietary software. Licensed to Corrosion platform users only.

Version History

1.0.0 (2026-02-15)

• Initial release
• NATS connectivity with token auth
• Process management (start/stop/restart)
• File operations (read/write/delete/list)
• SteamCMD integration
• Self-update capability
• Heartbeat monitoring
• Graceful shutdown handling