Introduction

Docker has revolutionized how we build, ship, and run applications. This tutorial will take you from Docker basics to advanced container orchestration, enabling you to create reproducible development and production environments.

Docker Installation and Setup

Install Docker on Ubuntu/Debian: curl -fsSL https://get.docker.com -o get-docker.sh && sudo sh get-docker.sh. Add user to docker group: sudo usermod -aG docker $USER. Verify installation: docker --version and docker run hello-world.

Understanding Docker Architecture

Docker uses client-server architecture. The Docker client talks to the Docker daemon, which manages containers, images, networks, and volumes. Images are read-only templates, containers are running instances, and registries store images.

Writing Your First Dockerfile

Dockerfile defines how to build images. Start with FROM (base image), add WORKDIR, COPY files, RUN commands, EXPOSE ports, and CMD/ENTRYPOINT for execution. Example Dockerfile for Node.js app: FROM node:18, WORKDIR /app, COPY package*./, RUN npm install, COPY ., CMD ["npm", "start"].

Managing Containers and Images

Essential commands: docker build -t myapp:1.0, docker run -d -p 3000:3000 myapp:1.0, docker ps, docker stop, docker rm, docker rmi. Use docker logs container_id for debugging and docker exec -it container_id bash for interactive access.

Docker Compose for Multi-Container Apps

docker-compose.yml defines services, networks, and volumes. Example for web + database: version '3.8', services: web (build: ., ports: "8080:80"), db (image: postgres, environment, volumes). Start with docker-compose up -d, stop with docker-compose down.

Volume Management and Persistence

Containers are ephemeral - use volumes for persistent data. Create volumes: docker volume create mydata. Mount in container: -v mydata:/app/data. Use bind mounts for development (./local:/app) and named volumes for production.

Networking in Docker

Default networks: bridge (default for standalone), host (no isolation), none (disable network). Create custom bridge networks for container communication: docker network create mynet. Attach containers with --network mynet. Use service names for DNS resolution.

Production Best Practices

Use multi-stage builds to reduce image size. Run as non-root user: USER appuser. Implement healthchecks: HEALTHCHECK --interval=30s CMD curl -f http://localhost/ || exit 1. Use .dockerignore files. Tag images with git commits or semantic versions.

Container Security

Scan images for vulnerabilities: docker scan myapp:1.0. Use trusted base images (official or verified publishers). Enable Docker Content Trust. Set resource limits (--memory, --cpus). Read-only root filesystem (--read-only). Drop unnecessary Linux capabilities.

Orchestration with Docker Swarm or Kubernetes

For production scaling, consider orchestration: Docker Swarm (simpler) or Kubernetes (industry standard). Deploy stacks, manage secrets, implement rolling updates, and configure service discovery and load balancing.

Conclusion

Docker mastery accelerates development and simplifies deployment. Start with single-container applications, then progress to docker-compose for local development, and finally orchestration for production. Regular practice and exploring Docker Hub will expand your skills.