Getting Started with Docker and CI/CD

What is Docker and Why Use It?

Docker containers package your application with its runtime and dependencies into a single unit. This ensures consistency between development, staging, and production and simplifies onboarding and deployment.

Writing a Good Dockerfile

Use a minimal base image (e.g. Alpine or distroless), run as non-root when possible, and leverage layer caching by ordering commands from least to most frequently changing. Multi-stage builds help keep the final image small by building in one stage and copying only artifacts to the next.

Multi-stage builds: use one stage for building (with dev dependencies) and a second stage for running (only production dependencies and built assets).

Docker Compose for Local Development

Define your app, database, cache, and other services in a docker-compose.yml. Use volumes for hot reload and env files for secrets. This gives every developer the same environment with a single command.

CI/CD with GitHub Actions

Create workflows that run on push or PR: lint, test, build Docker image, push to a registry, and optionally deploy to a cloud provider. Use secrets for registry credentials and environment-specific config. Caching dependencies and Docker layers speeds up pipelines.

Security and Best Practices

• Scan images for vulnerabilities (e.g. Trivy, Snyk)
• Pin base image tags and keep them updated
• Use .dockerignore to exclude unnecessary files
• Limit container resources (CPU, memory) in production