Painless Docker - 2nd Edition

What You Will Learn

This guide teaches Docker from the inside out. Not just how to use it, but how it actually works, why it behaves the way it does, and how to reason about it in real systems.

By the end of this guide:

• You will understand where containers come from, historically and technically. You will know how Linux primitives like namespaces, cgroups, and union filesystems evolved into modern containers, and where Docker fits in the broader container ecosystem alongside OCI, containerd, and runC.

• You will be able to mentally model Docker's internals. You will know what happens on the host when you run a container, where Docker stores data, how runtimes interact, and how the daemon, containerd, shim, and runC cooperate. This removes the "black box" effect that causes most Docker confusion.

• You will gain complete control of the Docker CLI. Not just commands, but the concepts behind containers, images, networks, and volumes. You will understand container lifecycles, signals, restart policies, port mappings, and advanced execution modes, including Docker-in-Docker.

• You will learn how to control resources precisely, including CPU and memory limits, reservations, swappiness, OOM behavior, and CPU pinning. You will know how Docker enforces constraints at the kernel level and how to diagnose resource-related failures.

• You will master Docker images and Dockerfiles. You will understand image layering, tags vs digests, intermediate images, and how Docker builds images step by step. You will write Dockerfiles that are smaller, faster, safer, and easier to maintain.

• You will learn how to optimize builds seriously, using multi-stage builds, BuildKit caching, context minimization, and base image selection. You will understand when Alpine, distroless, or heavier base images actually make sense.

• You will understand data management deeply. Volumes, bind mounts, tmpfs, initialization behavior, and data propagation will no longer be mysterious. You will know exactly when data is shared, copied, persisted, or lost.

• You will master Docker networking, from bridge networks to macvlan and host mode. You will understand how containers talk to each other, how traffic flows in and out, and how Docker's networking model differs from traditional networking.

• You will learn how to observe and troubleshoot Docker systems