OpenCPN Docker

Docker image for OpenCPN - a full-featured chartplotter and marine GPS navigation software, accessible via web browser using Selkies.

Overview

OpenCPN is a free and open-source chartplotter and navigation software for recreational sailors and boaters. This Docker image packages OpenCPN with Selkies, a web-native remote desktop platform, allowing you to access OpenCPN through any modern web browser without needing VNC clients or remote desktop software.

Features

• Browser-Based Access: Access OpenCPN from any device with a web browser
• No VNC Client Required: Uses WebRTC technology for low-latency streaming
• GPU Acceleration: Hardware-accelerated rendering for smooth chart display
• File Upload/Download: Easy chart management through web interface
• Multi-Architecture: Supports ARM64 (Raspberry Pi) and AMD64
• Persistent Storage: Configuration and charts stored in Docker volumes
• Night Mode Support: Includes xcalib for screen dimming

Quick Start

docker run -d \
  --name opencpn \
  -p 3020:3000 \
  -v opencpn-config:/config \
  --shm-size=1gb \
  ghcr.io/hatlabs/opencpn-docker:latest

Access OpenCPN at http://localhost:3020

Configuration

Volumes

• /config - OpenCPN configuration, charts, and user data

Ports

• 3000 - HTTP web interface (map to your preferred external port)
• 3001 - HTTPS web interface (optional, self-signed certificate)
• 8082 - WebSocket connection (used internally)

Environment Variables

Display Settings:

• CUSTOM_RES_W - Browser width resolution (default: 1920)
• CUSTOM_RES_H - Browser height resolution (default: 1080)
• SELKIES_ENABLE_RESIZE=true - Enable responsive resolution scaling

GPU Acceleration:

• DRI_NODE=/dev/dri/renderD128 - Enable hardware acceleration

Authentication (Optional):

• CUSTOM_USER - HTTP Basic auth username
• PASSWORD - HTTP Basic auth password

UI Customization:

• TITLE=OpenCPN - Browser tab title (default)
• SELKIES_ENABLE_CLIPBOARD_SYNC=true - Enable clipboard sharing

Using OpenCPN

First Launch

1. Access the web interface at your configured port
2. OpenCPN will launch automatically in the browser
3. Complete the initial setup wizard
4. Configure chart directories and data sources

Managing Charts

Upload Charts via Web Interface:

1. Click the folder icon in the Selkies toolbar
2. Use the upload feature to transfer chart files
3. Charts will be saved in /config/charts/
4. In OpenCPN, add the chart directory: Options → Charts → Add Directory

Alternative - Docker Volume:

# Copy charts directly to the volume
docker cp /path/to/charts opencpn:/config/charts/

NMEA Data Sources

Configure NMEA connections in OpenCPN:

• Network: Connect to Signal K or other NMEA servers
• Serial: Mount serial devices with --device=/dev/ttyUSB0
• File Playback: Upload NMEA log files for replay

Hardware Acceleration

The container uses software rendering by default, which should work on all systems.

GPU Acceleration Issues

While hardware acceleration via /dev/dri is theoretically possible, it currently causes display issues on some systems (blank screen). This is a known limitation with the Selkies web desktop stack.

If you want to experiment with GPU acceleration:

docker run -d \
  --name opencpn \
  -p 3020:3000 \
  -v opencpn-config:/config \
  --device=/dev/dri:/dev/dri \
  --shm-size=1gb \
  -e DRI_NODE=/dev/dri/renderD128 \
  ghcr.io/hatlabs/opencpn-docker:latest

Requirements:

• Intel or AMD GPU with DRI3 support
• Proper GPU drivers installed on host
• May result in blank screen (see known limitations below)

Note: Software rendering performance is generally adequate for chart plotting. Only experiment with GPU acceleration if you experience performance issues.

Advanced Usage

With Authentication

docker run -d \
  --name opencpn \
  -p 3021:3001 \
  -v opencpn-config:/config \
  -e CUSTOM_USER=admin \
  -e PASSWORD=your-secure-password \
  --shm-size=1gb \
  ghcr.io/hatlabs/opencpn-docker:latest

Custom Resolution

docker run -d \
  --name opencpn \
  -p 3021:3001 \
  -v opencpn-config:/config \
  -e CUSTOM_RES_W=2560 \
  -e CUSTOM_RES_H=1440 \
  --shm-size=1gb \
  ghcr.io/hatlabs/opencpn-docker:latest

Building Locally

docker build -t opencpn:local .

For multi-architecture builds:

docker buildx build --platform linux/amd64,linux/arm64 -t opencpn:local .

Documentation

• OpenCPN Official Website
• OpenCPN User Manual
• Selkies Project
• linuxserver.io Selkies Baseimage

Troubleshooting

Black Screen or No Display

• Ensure --shm-size=1gb is set (required for Chromium-based Selkies)
• Check browser console for WebRTC errors
• Verify port 3000 is accessible

Poor Performance

• Software rendering is used by default (GPU acceleration has compatibility issues)
• Increase allocated resources (CPU/RAM)
• Reduce resolution with CUSTOM_RES_W and CUSTOM_RES_H environment variables

Charts Not Appearing

• Verify charts are in /config/charts/ directory
• In OpenCPN: Options → Charts → Add Directory
• Force chart database rebuild if needed

License

This Docker image is licensed under GPL-2.0, matching the upstream OpenCPN project. See LICENSE for details.

OpenCPN is licensed under GPL-2.0. Selkies and related components have their own licenses.

Contributing

Contributions are welcome! Please open an issue or pull request on the GitHub repository.

Support

For issues with this Docker image, open an issue on GitHub. For OpenCPN-specific questions, refer to the OpenCPN documentation or OpenCPN forums.