Quick one-liner: Pre-built images are convenient until they break. A Dockerfile turns your app into a portable, reproducible artifact you can fix, rebuild, and own. 🤔 Why This Matters In episode 10, we fixed the startup race. Ghost now waits for MySQL to be genuinely ready before starting. The stack is stable. But after docker compose down --volumes , you rebuild from scratch: new theme, default config, all manual setup repeated. The image pulled from Docker Hub does not remember your changes. That is not a Ghost problem. That is what it looks like when you do not own the image. A Dockerfile is how you own it. You start from a base, install what you need, bake in configuration, and define exactly what runs when the container starts. The result is an artifact that rebuilds cleanly and consistently every time. This episode covers the fundamentals: FROM , WORKDIR , COPY , RUN , EXPOSE , and CMD . The example is a Flask app — small enough to understand, realistic enough to matter.…