MCP Server: Docker Command Runner

This MCP (Model Context Protocol) server provides a secure interface for running commands inside Docker containers. It acts as a privileged sidecar that can execute arbitrary commands within specified Docker Compose service containers.

Features

• STDIO-based MCP transport for integration with Claude and other MCP clients
• Execute commands in any Docker Compose service container
• Real-time capture of stdout/stderr output
• Secure container allowlist configuration
• Configurable timeouts for long-running commands
• Clear error messages for common Docker issues
• Minimal dependencies and secure by design

Installation

Via NPX (Recommended)

Run the MCP server directly without cloning:

npx mcp-server-docker

Or install globally:

npm install -g mcp-server-docker
mcp-server-docker

As a Docker Service

Add the following to your docker-compose.yml:

services:
  mcp-docker:
    build: ./mcp-server-docker
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    ports:
      - "3001:3000"  # Expose MCP server
    environment:
      - COMPOSE_PROJECT_NAME=${COMPOSE_PROJECT_NAME}
      - DEFAULT_SERVICE=app
      - COMPOSE_FILE=docker-compose.yml
      - PORT=3000
    networks:
      - your-network

For Local Development

cd mcp-server-docker
npm install
npm run build

Configuration

The server accepts the following environment variables:

• ALLOWED_CONTAINERS: Comma-separated list of allowed service:container pairs (e.g., "app:myapp_container,db:mydb_container")
• DEFAULT_SERVICE: Default service to run commands in (default: "laravel_app")
• COMMAND_TIMEOUT: Command timeout in milliseconds (default: 300000)

MCP Tool: run_command

The server exposes a single tool called run_command:

Input Schema

{
  "command": "string (required) - The command to execute",
  "service": "string (optional) - Docker service name"
}

Example Usage

{
  "command": "npm test",
  "service": "frontend"
}

Response Format

The tool returns the command output with the following structure:

• Standard output (if any)
• Standard error (if any, prefixed with [stderr])
• Exit code

Usage

The server uses STDIO transport for MCP communication. When run with npx mcp-server-docker, it will:

1. Parse environment variables for allowed containers
2. Start the MCP server listening on stdin/stdout
3. Log startup information to stderr
4. Wait for MCP protocol messages

Security Notes

• This server requires access to the Docker socket - ensure Docker is running and accessible
• No command filtering is applied - relies on container isolation for security
• Commands timeout after 5 minutes by default
• Only allowed containers (configured via ALLOWED_CONTAINERS) can be accessed

Development

# Run in development mode
npm run dev

# Build TypeScript
npm run build

# Run tests
npm test

Troubleshooting

Common Errors

1. "Cannot connect to Docker daemon": Ensure Docker is running and the socket is mounted
2. "Service not found": Check that the service name exists in your docker-compose.yml
3. "Command timed out": Command exceeded 5-minute timeout, consider breaking it into smaller operations