Docker Environment Setup

The Docker adapter enables seamless command execution within Docker containers, supporting both existing containers and ephemeral runs. It provides full lifecycle management, volume mounting, and container orchestration capabilities.

Installation and Prerequisites

Docker Installation

Ensure Docker is installed and accessible:

# Check Docker installation
docker --version
docker info

The Docker adapter automatically detects Docker installations in common locations:

• /usr/local/bin/docker (Docker Desktop on macOS)
• /usr/bin/docker (Linux)
• /opt/homebrew/bin/docker (Homebrew on macOS)

Basic Configuration

import { $ } from '@xec-sh/core';

// Basic Docker execution using existing container
const result = await $({
  adapterOptions: {
    type: 'docker',
    container: 'my-container'
  }
})`ls -la /app`;

console.log(result.stdout);

Configuration Options

Adapter Configuration

Configure the Docker adapter with various options:

import { DockerAdapter } from '@xec-sh/core';

const docker = new DockerAdapter({
  // Docker daemon configuration
  socketPath: '/var/run/docker.sock',  // Unix socket path
  host: 'localhost',                   // Docker host
  port: 2376,                         // Docker port
  version: '1.41',                    // API version
  
  // Default execution options
  defaultExecOptions: {
    User: '1000:1000',                // Default user:group
    WorkingDir: '/app',               // Default working directory
    Env: ['NODE_ENV=production'],     // Default environment variables
    Privileged: false,                // Privileged mode
    AttachStdin: true,
    AttachStdout: true,
    AttachStderr: true,
    Tty: false
  },
  
  // Auto-creation configuration
  autoCreate: {
    enabled: true,                    // Auto-create containers
    image: 'alpine:latest',           // Default image
    autoRemove: true,                 // Remove after execution
    volumes: ['/tmp:/tmp:rw']         // Default volumes
  }
});

// Use the configured adapter
const result = await docker.execute({
  command: 'whoami',
  adapterOptions: {
    type: 'docker',
    container: 'my-app'
  }
});

Container Options

Specify container-specific execution options:

// Execute in existing container
await $({
  adapterOptions: {
    type: 'docker',
    container: 'web-server',
    user: 'www-data',
    workdir: '/var/www/html',
    tty: true
  }
})`npm test`;

// Execute with environment variables
await $({
  env: {
    NODE_ENV: 'development',
    DEBUG: 'app:*'
  },
  adapterOptions: {
    type: 'docker',
    container: 'node-app'
  }
})`node server.js`;

Execution Modes

Exec Mode

Execute commands in existing containers:

// Execute in running container
const logs = await $({
  adapterOptions: {
    type: 'docker',
    container: 'nginx-proxy',
    runMode: 'exec'  // Explicit exec mode
  }
})`tail -f /var/log/nginx/access.log`;

Run Mode

Create ephemeral containers for command execution:

// Run command in new container
const result = await $({
  adapterOptions: {
    type: 'docker',
    container: 'test-runner',  // Container name (optional)
    image: 'node:18-alpine',   // Required for run mode
    runMode: 'run',
    volumes: ['./src:/app/src:ro'],
    workdir: '/app',
    autoRemove: true  // Clean up after execution
  }
})`npm test`;

// Auto-detected run mode (when image is specified)
await $({
  adapterOptions: {
    type: 'docker',
    image: 'ubuntu:22.04',  // Image triggers run mode
    volumes: ['./data:/data']
  }
})`ls -la /data`;

Environment Variables

Setting Environment Variables

Pass environment variables to containers:

// Method 1: Command-level environment
await $({
  env: {
    API_KEY: 'secret-key',
    DB_HOST: 'database.local',
    PORT: '3000'
  },
  adapterOptions: {
    type: 'docker',
    container: 'api-server'
  }
})`printenv | grep -E "API_KEY|DB_HOST|PORT"`;

// Method 2: Adapter default environment
const docker = new DockerAdapter({
  defaultExecOptions: {
    Env: [
      'NODE_ENV=production',
      'LOG_LEVEL=info'
    ]
  }
});

Environment Variable Precedence

Environment variables are merged with the following precedence:

1. Command-level env (highest priority)
2. Adapter defaultExecOptions.Env
3. Global defaultEnv configuration

// Demonstrates environment variable precedence
const docker = new DockerAdapter({
  defaultEnv: { GLOBAL: 'global-value' },
  defaultExecOptions: {
    Env: ['ADAPTER=adapter-value']
  }
});

await $({
  env: { COMMAND: 'command-value' },
  adapterOptions: {
    type: 'docker',
    container: 'env-test'
  }
})`printenv | sort`;
// Output includes: GLOBAL=global-value, ADAPTER=adapter-value, COMMAND=command-value

Working Directories

Setting Working Directory

Configure the working directory for command execution:

// Set working directory
await $({
  adapterOptions: {
    type: 'docker',
    container: 'dev-container',
    workdir: '/workspace/project'
  }
})`pwd && ls -la`;

// Relative paths in container
await $({
  adapterOptions: {
    type: 'docker',
    container: 'builder',
    workdir: '/build'
  }
})`
  ./configure --prefix=/usr/local
  make && make install
`;

User and Permissions

Running as Specific User

Execute commands as different users:

// Run as specific user
await $({
  adapterOptions: {
    type: 'docker',
    container: 'app-container',
    user: 'appuser'  // Username or UID
  }
})`whoami && id`;

// Run as user:group
await $({
  adapterOptions: {
    type: 'docker',
    container: 'data-processor',
    user: '1000:1000'  // UID:GID
  }
})`touch /tmp/test-file && ls -la /tmp/test-file`;

// Default user from adapter configuration
const docker = new DockerAdapter({
  defaultExecOptions: {
    User: 'nobody:nogroup'
  }
});

TTY and Interactive Mode

TTY Configuration

Configure TTY and interactive modes:

// Interactive TTY mode
await $({
  stdin: 'echo "Hello from stdin"',
  adapterOptions: {
    type: 'docker',
    container: 'interactive-app',
    tty: true
  }
})`cat`;

// Non-TTY mode for scripting
await $({
  adapterOptions: {
    type: 'docker',
    container: 'batch-processor',
    tty: false
  }
})`
  for i in {1..5}; do
    echo "Processing batch $i"
    sleep 1
  done
`;

The adapter automatically detects TTY support and optimizes settings:

• Interactive mode enabled when stdin is provided or TTY requested
• TTY mode only enabled when environment supports it
• Warnings shown when TTY requested but not available

Container Validation

Security Validation

The Docker adapter performs security validation on container names:

// Valid container names
const validNames = [
  'my-container',
  'web_server',
  'app-v1.2.3',
  'namespace_app'
];

// Invalid container names (will throw errors)
const invalidNames = [
  '',                    // Empty name
  'container; rm -rf /', // Command injection
  '../container',        // Path traversal
  'container|malicious', // Shell metacharacters
  '/absolute/path'       // Absolute path
];

// Container names must match: [a-zA-Z0-9][a-zA-Z0-9_.-]*
try {
  await $({
    adapterOptions: {
      type: 'docker',
      container: 'valid-name'
    }
  })`echo "Safe execution"`;
} catch (error) {
  console.error('Container validation failed:', error.message);
}

Error Handling

Common Error Scenarios

Handle Docker-specific errors:

import { DockerError } from '@xec-sh/core';

try {
  await $({
    adapterOptions: {
      type: 'docker',
      container: 'non-existent'
    }
  })`echo "test"`;
} catch (error) {
  if (error instanceof DockerError) {
    console.error('Docker error:', error.container, error.operation, error.message);
  }
}

// Handle container not found
try {
  await $({
    adapterOptions: {
      type: 'docker',
      container: 'missing-container'
    }
  })`ls /app`;
} catch (error) {
  if (error.message.includes('not found')) {
    console.log('Container does not exist');
    // Auto-create or handle gracefully
  }
}

Auto-Creation Error Handling

Configure automatic container creation:

const docker = new DockerAdapter({
  autoCreate: {
    enabled: true,
    image: 'alpine:latest',
    autoRemove: true
  }
});

// Will auto-create container if it doesn't exist
try {
  const result = await docker.execute({
    command: 'echo',
    args: ['Container auto-created'],
    adapterOptions: {
      type: 'docker',
      container: 'auto-created-container'
    }
  });
  console.log('Success:', result.stdout);
} catch (error) {
  console.error('Auto-creation failed:', error.message);
}

Availability Check

Docker Environment Detection

Check Docker availability before execution:

import { DockerAdapter } from '@xec-sh/core';

const docker = new DockerAdapter();

// Check if Docker is available
const isAvailable = await docker.isAvailable();
if (!isAvailable) {
  console.error('Docker is not available');
  process.exit(1);
}

// Check Docker version
const version = await $({
  adapterOptions: { type: 'docker', container: 'temp' }
})`docker --version`.catch(() => null);

if (version?.exitCode === 0) {
  console.log('Docker version:', version.stdout.trim());
}

Resource Cleanup

Automatic Cleanup

The Docker adapter automatically manages temporary containers:

const docker = new DockerAdapter({
  autoCreate: {
    enabled: true,
    autoRemove: true  // Automatically remove temporary containers
  }
});

// Temporary containers are automatically cleaned up
await docker.execute({
  command: 'echo',
  args: ['Temporary execution'],
  adapterOptions: {
    type: 'docker',
    container: 'temp-container'
  }
});

// Manual cleanup
await docker.dispose(); // Cleans up all temporary containers

Event Monitoring

Monitor Docker operations with events:

docker.on('docker:run', (event) => {
  console.log('Container run:', event.image, event.container);
});

docker.on('docker:exec', (event) => {
  console.log('Container exec:', event.container, event.command);
});

docker.on('temp:cleanup', (event) => {
  console.log('Cleaning up:', event.path);
});

// Execute command with event monitoring
await $({
  adapterOptions: {
    type: 'docker',
    image: 'alpine',
    container: 'monitored'
  }
})`echo "Monitored execution"`;

Best Practices

Performance Optimization

• Use existing containers for repeated executions
• Enable connection reuse for multiple operations
• Use appropriate base images (alpine for minimal overhead)
• Configure resource limits appropriately

Security Considerations

• Always validate container names
• Use non-root users when possible
• Mount volumes with appropriate permissions
• Avoid passing secrets in environment variables
• Use secure secret management systems

Resource Management

• Enable auto-removal for ephemeral containers
• Monitor container resource usage
• Clean up unused images and containers
• Use multi-stage builds for smaller images

// Example of optimized Docker usage
const docker = new DockerAdapter({
  autoCreate: {
    enabled: true,
    image: 'alpine:latest',
    autoRemove: true
  },
  defaultExecOptions: {
    User: '1000:1000',  // Non-root user
    WorkingDir: '/workspace'
  }
});

// Efficient execution pattern
const results = await Promise.all([
  docker.execute({
    command: 'echo',
    args: ['Task 1'],
    adapterOptions: { type: 'docker', container: 'worker-1' }
  }),
  docker.execute({
    command: 'echo', 
    args: ['Task 2'],
    adapterOptions: { type: 'docker', container: 'worker-2' }
  })
]);

// Cleanup
await docker.dispose();