Introduction to Docker and Container Orchestration

What is Docker?

Docker is an open-source platform that enables developers to package applications and their dependencies into lightweight, portable containers. Containers share the host OS kernel, making them far more resource-efficient than traditional virtual machines.

Core Concepts

Image: A read-only blueprint for a container. Container: A running instance of an image. Dockerfile: A script that defines how to build an image. Registry: A storage hub for images (e.g. Docker Hub).

Writing Your First Dockerfile

FROM php:8.2-fpm-alpine
WORKDIR /var/www/html
COPY composer.json composer.lock ./
RUN composer install --no-dev --optimize-autoloader
COPY . .
EXPOSE 9000
CMD ["php-fpm"]

Docker Compose for Multi-Container Apps

Most real-world applications need multiple services — a web server, a database, a cache. Docker Compose lets you define them all in a single docker-compose.yml and spin them up with one command: docker compose up -d.

services:
  app:
    build: .
    depends_on: [db, redis]
  db:
    image: mysql:8.0
    environment:
      MYSQL_ROOT_PASSWORD: secret
  redis:
    image: redis:7-alpine

Networking and Volumes

Containers communicate via Docker networks. Persist data across restarts using named volumes. Never store persistent data inside a container layer.

Introduction to Kubernetes

Kubernetes (K8s) takes container orchestration to production scale. It handles scheduling, self-healing, rolling updates, and horizontal pod autoscaling across a cluster of nodes.

Conclusion

Docker eliminates "works on my machine" problems and Kubernetes ensures your containerised app runs reliably at scale. Investing time in these tools pays dividends throughout your career.