We like spreading the word about linting tools that actually help you find issues rather than just shortcut style disputes in the team. Hadolint is one of those tools — it helps find common issues in Dockerfiles. We find it to be fast, accurate and with good documentation. It explains both how to fix an issue and why it's an issue in the first place, thus nudging Dockerfile authors toward good practices. Incidentally, Hadolint is built on top of ShellCheck, which we recommend in its own right for checking your shell scripts.