Roadmap / Docker Deep Dive
A comprehensive Docker roadmap covering container fundamentals, image building, multi-stage builds, Docker Compose, networking, storage, security, registry management, CI/CD integration, and orchestration concepts — from first container to production-grade workflows.
Step 1 • Foundations
Understand the problem containers solve — dependency hell ("works on my machine"), environment drift between dev/staging/prod, slow VM startup times, and wasted resources. Containers use Linux namespaces (process isolation) and cgroups (resource limits) to provide lightweight isolation without a full OS. Understand the difference between containers (runtime) and images (blueprint), and how Docker wraps these Linux primitives.
Step 2 • Foundations
Install Docker Desktop and learn the essential CLI commands — docker run (flags: -d detached, -p port mapping, -e env vars, --name, --rm auto-remove, -v volume mount), docker ps (list running containers), docker images, docker stop/start/kill, docker rm/rmi, docker exec (run commands inside a running container), docker logs (--follow, --tail), and docker inspect for detailed metadata.
Step 3 • Foundations
Understand how Docker images work — an image is a read-only stack of layers (each Dockerfile instruction adds a layer), containers add a writable layer on top. Learn image tags (repository:tag:digest), how docker pull resolves tags, layer caching (shared between images using the same base), and how to push/pull from Docker Hub, GitHub Container Registry (GHCR), AWS ECR, and private registries.
Step 4 • Building
Write Dockerfiles that build correctly and efficiently — FROM (choosing base images: full OS vs slim vs distroless), RUN (combine commands with && to minimize layers), COPY vs ADD (prefer COPY), WORKDIR, ENV and ARG (build-time vs runtime), EXPOSE, CMD vs ENTRYPOINT (CMD provides defaults, ENTRYPOINT sets the executable), and .dockerignore to exclude node_modules, .git, and build artifacts from the build context.
Step 5 • Building
Understand and control Docker's layer cache — cache invalidation (any layer change invalidates all subsequent layers), ordering instructions for maximum cache reuse (install dependencies before copying source code), BuildKit cache mounts (--mount=type=cache for package managers), and using docker buildx bake for parallel multi-target builds. Measure build times and image sizes.
Step 6 • Building
Dramatically reduce production image size with multi-stage builds — use a full build environment (Node, Go, Java) for compilation and a minimal runtime image (node:alpine, distroless, or scratch) for production. Copy only the compiled artifacts between stages with COPY --from=build. Understand why smaller images mean fewer vulnerabilities, faster pulls, and less attack surface.
Step 7 • Compose
Orchestrate multi-container development environments with Docker Compose — define services (app, postgres, redis, worker), configure service dependencies (depends_on with health checks), port mappings, environment variables, named volumes for database persistence, and networks. Use override files (docker-compose.override.yml) to customize for each environment. Run the entire stack with a single command.
Step 8 • Compose
Understand Docker's three storage types — named volumes (managed by Docker, persist across container restarts, ideal for databases and uploads), bind mounts (host path → container path, for development hot-reload but problematic in production), and tmpfs (in-memory, no persistence). Know how to back up, restore, and migrate named volumes, and why container root filesystems are ephemeral.
Step 9 • Networking
Understand how containers communicate — the bridge driver (default, containers on the same network communicate by service name), host networking (container uses host network stack, no isolation), overlay networks (multi-host, used with Swarm), published ports (-p 8080:80 maps host port to container port), and how Compose creates isolated bridge networks per project. Debug connectivity with docker network inspect.
Step 10 • Operations
Diagnose and fix container problems — docker logs (--follow, --since, --until), docker exec -it (interactive debugging session), docker inspect (full JSON metadata for networks, mounts, env), docker stats (real-time CPU/memory/network), docker events (real-time daemon events), and docker system df/prune (clean up dangling images, stopped containers, unused volumes to reclaim disk space).
Step 11 • Operations
Make containers production-ready — HEALTHCHECK instruction (command, interval, timeout, retries, start-period), dependency on health in Compose (depends_on: condition: service_healthy), liveness vs readiness probes (Kubernetes model), graceful shutdown (handle SIGTERM in your app to drain requests before stopping — especially important in Node.js), and init processes (tini) to correctly forward signals in containers.
Step 12 • Security
Harden Docker usage — run containers as a non-root user (USER instruction), use read-only root filesystem (--read-only), drop Linux capabilities (--cap-drop ALL, add back only needed ones), scan images for CVEs with Docker Scout or Trivy, use minimal base images (distroless, scratch), manage secrets properly (Docker secrets or build-time ARGs for non-sensitive config), and understand the OWASP Docker Security Cheat Sheet.
Step 13 • Building
Build images that run on both amd64 (x86 cloud servers) and arm64 (Apple Silicon M-series, Raspberry Pi, AWS Graviton). Use docker buildx with QEMU emulation for cross-compilation, --platform linux/amd64,linux/arm64, and Docker Build Cloud for faster multi-platform builds. Publish a multi-platform image manifest to a registry and verify it runs on both architectures.
Step 14 • CI/CD
Integrate Docker builds into GitHub Actions — build and push to GHCR on every merge (docker/build-push-action), tag with semantic versions and commit SHAs, cache layers between CI runs (cache-from/cache-to), add vulnerability scanning (Trivy action), generate SBOM (Software Bill of Materials), sign images with cosign (SLSA provenance), and block deployments if critical CVEs are found.
Step 15 • deployment
Push and pull images from Docker Hub, AWS ECR, GitHub Container Registry (GHCR), and Google Artifact Registry. Learn image tagging strategies (semantic versioning, :latest, SHA digest), image scanning for vulnerabilities with Trivy or Snyk, and authenticate securely with docker login or credential helpers.
Step 16 • Production
Use Docker Compose for staging/single-server production deployments — configure production-specific overrides (docker-compose.prod.yml), deploy with Watchtower for automatic image updates, manage secrets with Docker secrets (swarm mode) or environment-injected secrets, set resource limits (cpus and memory in deploy.resources), and understand when Compose is enough vs when you need Kubernetes.
Step 17 • Ship It
Understand where Docker ends and orchestration begins — scheduling containers across multiple nodes, service discovery (how services find each other in a cluster), auto-scaling (add pods when CPU > 80%), self-healing (restart failed pods), rolling deployments (update without downtime), and resource quotas. Explore Docker Swarm (simpler, built into Docker) and Kubernetes (industry standard, more complex but more capable).
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