Docker Containerization Skill

Docker Containerization Skill

Overview

Generate production-ready Docker configurations for modern web applications, particularly Next.js and Node.js projects. This skill provides Dockerfiles, docker-compose setups, bash scripts for container management, and comprehensive deployment guides for various orchestration platforms.

Core Capabilities

1. Dockerfile Generation

Create optimized Dockerfiles for different environments:

Production (assets/​Dockerfile.production):

• Multi-stage build reducing image size by 85%
• Alpine Linux base (~180MB final image)
• Non-root user execution for security
• Health checks and resource limits

Development (assets/​Dockerfile.development):

• Hot reload support
• All dev dependencies included
• Volume mounts for live code updates

Nginx Static (assets/​Dockerfile.nginx):

• Static export optimization
• Nginx reverse proxy included
• Smallest possible footprint

2. Docker Compose Configuration

Multi-container orchestration with assets/​docker-compose.yml:

• Development and production services
• Network and volume management
• Health checks and logging
• Restart policies

3. Bash Scripts for Container Management

docker-build.sh - Build images with comprehensive options:

./​docker-build.sh -e prod -t v1.0.0
./​docker-build.sh -n my-app --no-cache --platform linux/​amd64

docker-run.sh - Run containers with full configuration:

./​docker-run.sh -i my-app -t v1.0.0 -d
./​docker-run.sh -p 8080:3000 --env-file .env.production

docker-push.sh - Push to registries (Docker Hub, ECR, GCR, ACR):

./​docker-push.sh -n my-app -t v1.0.0 --repo username/​my-app
./​docker-push.sh -r gcr.io/​project --repo my-app --also-tag stable

docker-cleanup.sh - Free disk space:

./​docker-cleanup.sh --all --dry-run  # Preview cleanup
./​docker-cleanup.sh --containers --images  # Clean specific resources

4. Configuration Files

• .dockerignore: Excludes unnecessary files (node_modules, .git, logs)
• nginx.conf: Production-ready Nginx configuration with compression, caching, security headers

5. Reference Documentation

docker-best-practices.md covers:

• Multi-stage builds explained
• Image optimization techniques (50-85% size reduction)
• Security best practices (non-root users, vulnerability scanning)
• Performance optimization
• Health checks and logging
• Troubleshooting guide

container-orchestration.md covers deployment to:

• Docker Compose (local development)
• Kubernetes (enterprise scale with auto-scaling)
• Amazon ECS (AWS-native orchestration)
• Google Cloud Run (serverless containers)
• Azure Container Instances
• Digital Ocean App Platform

Includes configuration examples, commands, auto-scaling setup, and monitoring.

Workflow Decision Tree

1. What environment?

• Development → Dockerfile.development (hot reload, all dependencies)
• Production → Dockerfile.production (minimal, secure, optimized)
• Static Export → Dockerfile.nginx (smallest footprint)

2. Single or Multi-container?

• Single → Generate Dockerfile only
• Multi → Generate docker-compose.yml (app + database, microservices)

3. Which registry?

• Docker Hub → docker.io/​username/​image
• AWS ECR → 123456789012.dkr.ecr.region.amazonaws.com/​image
• Google GCR → gcr.io/​project-id/​image
• Azure ACR → registry.azurecr.io/​image

4. Deployment platform?

• Kubernetes → See references/​container-orchestration.md K8s section
• ECS → See ECS task definition examples
• Cloud Run → See deployment commands
• Docker Compose → Use provided compose file

5. Optimizations needed?

• Image size → Multi-stage builds, Alpine base
• Build speed → Layer caching, BuildKit
• Security → Non-root user, vulnerability scanning
• Performance → Resource limits, health checks

Usage Examples

Example 1: Containerize Next.js App for Production

User: "Containerize my Next.js app for production"

Steps:

1. Copy assets/​Dockerfile.production to project root as Dockerfile
2. Copy assets/​.dockerignore to project root
3. Build: ./​docker-build.sh -e prod -n my-app -t v1.0.0
4. Test: ./​docker-run.sh -i my-app -t v1.0.0 -p 3000:3000 -d
5. Push: ./​docker-push.sh -n my-app -t v1.0.0 --repo username/​my-app

Example 2: Development with Docker Compose

User: "Set up Docker Compose for local development"

Steps:

1. Copy assets/​Dockerfile.development and assets/​docker-compose.yml to project
2. Customize services in docker-compose.yml
3. Start: docker-compose up -d
4. Logs: docker-compose logs -f app-dev

Example 3: Deploy to Kubernetes

User: "Deploy my containerized app to Kubernetes"

Steps:

1. Build and push image to registry
2. Review references/​container-orchestration.md Kubernetes section
3. Create K8s manifests (deployment, service, ingress)
4. Apply: kubectl apply -f deployment.yaml
5. Verify: kubectl get pods && kubectl logs -f deployment/​app

Example 4: Deploy to AWS ECS

User: "Deploy to AWS ECS Fargate"

Steps:

1. Build and push to ECR
2. Review references/​container-orchestration.md ECS section
3. Create task definition JSON
4. Register: aws ecs register-task-definition --cli-input-json file://task-def.json
5. Create service: aws ecs create-service --cluster my-cluster --service-name app --desired-count 3

Best Practices

Security

✅ Use multi-stage builds for production ✅ Run as non-root user ✅ Use specific image tags (not latest) ✅ Scan for vulnerabilities ✅ Never hardcode secrets ✅ Implement health checks

Performance

✅ Optimize layer caching order ✅ Use Alpine images (~85% smaller) ✅ Enable BuildKit for parallel builds ✅ Set resource limits ✅ Use compression

Maintainability

✅ Add comments for complex steps ✅ Use build arguments for flexibility ✅ Keep Dockerfiles DRY ✅ Version control all configs ✅ Document environment variables

Troubleshooting

Image too large (>500MB) → Use multi-stage builds, Alpine base, comprehensive .dockerignore

Build is slow → Optimize layer caching, use BuildKit, review dependencies

Container exits immediately → Check logs: docker logs container-name → Verify CMD/​ENTRYPOINT, check port conflicts

Changes not reflecting → Rebuild without cache, check .dockerignore, verify volume mounts

Quick Reference

# Build
./​docker-build.sh -e prod -t latest

# Run
./​docker-run.sh -i app -t latest -d

# Logs
docker logs -f app

# Execute
docker exec -it app sh

# Cleanup
./​docker-cleanup.sh --all --dry-run  # Preview
./​docker-cleanup.sh --all            # Execute

Integration with CI/​CD

GitHub Actions

- run: |
    chmod +x docker-build.sh docker-push.sh
    ./​docker-build.sh -e prod -t ${{ github.sha }}
    ./​docker-push.sh -n app -t ${{ github.sha }} --repo username/​app

GitLab CI

build:
  script:
    - chmod +x docker-build.sh
    - ./​docker-build.sh -e prod -t $CI_COMMIT_SHA

Resources

Scripts (scripts/)

Production-ready bash scripts with comprehensive features:

• docker-build.sh - Build images (400+ lines, colorized output)
• docker-run.sh - Run containers (400+ lines, auto conflict resolution)
• docker-push.sh - Push to registries (multi-registry support)
• docker-cleanup.sh - Clean resources (dry-run mode, selective cleanup)

References (references/)

Detailed documentation loaded as needed:

• docker-best-practices.md - Comprehensive Docker best practices (~500 lines)
• container-orchestration.md - Deployment guides for 6+ platforms (~600 lines)

Assets (assets/)

Ready-to-use templates:

• Dockerfile.production - Multi-stage production Dockerfile
• Dockerfile.development - Development Dockerfile
• Dockerfile.nginx - Static export with Nginx
• docker-compose.yml - Multi-container orchestration
• .dockerignore - Optimized exclusion rules
• nginx.conf - Production Nginx configuration