Docker

roadmap.sh: https://roadmap.sh/docker

Suggested path through the Docker nodes. Each node links to its lesson when written.

Nodes

Foundations

• What are containers
• Need for containerization
• Bare metal vs VMs vs containers
• Docker vs other container engines
• The underlying technologies
• Namespaces
• cgroups
• Union filesystems

Installation & setup

• Installing Docker
• Docker Desktop
• Docker Engine
• Understanding the Docker ecosystem

Docker fundamentals

• Docker architecture
• Docker daemon
• Docker client (CLI)
• Docker registries
• Images vs containers

Working with images

• Pulling images
• Finding images on Docker Hub
• Image tags and versions
• Inspecting images
• Image layers
• Listing and removing images

Building images

• Writing a Dockerfile
• Dockerfile instructions (FROM, RUN, CMD, ENTRYPOINT)
• COPY vs ADD
• ENV and ARG
• WORKDIR, EXPOSE, VOLUME
• Build context and .dockerignore
• Multi-stage builds
• BuildKit
• Layer caching and build optimization
• Image size optimization

Running containers

• docker run and its flags
• Container lifecycle (start, stop, restart, rm)
• Detached vs foreground mode
• Naming containers
• Interactive containers and exec
• Viewing logs
• Inspecting containers
• Restart policies
• Resource limits (CPU, memory)

Data persistence

• Ephemeral container filesystem
• Volumes
• Bind mounts
• tmpfs mounts
• Managing volumes

Networking

• Container networking basics
• Bridge network
• Host network
• None network
• Overlay network
• Port mapping and publishing
• DNS and service discovery
• Custom networks

Docker Compose

• What is Docker Compose
• compose.yaml structure
• Defining services
• Networks and volumes in Compose
• Environment variables and .env
• Depends_on and healthchecks
• Compose profiles
• Scaling services

Registries & distribution

• Docker Hub
• Pushing images
• Private registries
• Self-hosted registry
• Tagging strategy
• Image signing

Security

• Running as non-root user
• Least privilege and capabilities
• Image vulnerability scanning
• Secrets management
• Read-only filesystems
• Image provenance and trust
• Resource isolation

Best practices & production

• Dockerfile best practices
• Healthchecks
• Logging drivers
• Monitoring containers
• Container orchestration (overview)
• Docker Swarm
• CI/CD with Docker
• Developer experience and dev containers

Resources

See resources.md.

Project ideas

• Containerize a multi-service web app (frontend, API, Postgres) with a single Docker Compose file and a one-command compose up dev setup.
• Write an optimized multi-stage Dockerfile for a compiled-language service, then measure and shrink the final image size below 50 MB.
• Build a CI pipeline that lints the Dockerfile, scans the image for vulnerabilities, and pushes a tagged image to a private registry on each commit.