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:

• Copy assets/Dockerfile.production to project root as Dockerfile

• Copy assets/.dockerignore to project root

• Build: ./docker-build.sh -e prod -n my-app -t v1.0.0

• Test: ./docker-run.sh -i my-app -t v1.0.0 -p 3000:3000 -d

• 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:

• Copy assets/Dockerfile.development and assets/docker-compose.yml to project

• Customize services in docker-compose.yml

• Start: docker-compose up -d

• Logs: docker-compose logs -f app-dev

Example 3: Deploy to Kubernetes

User: "Deploy my containerized app to Kubernetes"

Steps:

• Build and push image to registry

• Review references/container-orchestration.md Kubernetes section

• Create K8s manifests (deployment, service, ingress)

• Apply: kubectl apply -f deployment.yaml

• Verify: kubectl get pods && kubectl logs -f deployment/app

Example 4: Deploy to AWS ECS

User: "Deploy to AWS ECS Fargate"

Steps:

• Build and push to ECR

• Review references/container-orchestration.md ECS section

• Create task definition JSON

• Register: aws ecs register-task-definition --cli-input-json file://task-def.json

• 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