ENTRYPOINT vs CMD in Dockerfile: Differences and Best Practices
Understand the fundamental differences between ENTRYPOINT and CMD directives and how to combine them for flexible container CLIs.
ENTRYPOINT ["node", "server.js"]
CMD ["--port", "3000"]Step-by-Step Execution Guide
ENTRYPOINT ["executable", "param1", "param2"]JSON array syntax does not invoke a shell wrapper, allowing the process to receive SIGTERM signals properly (PID 1).
CMD executable param1 param2Runs command as "/bin/sh -c executable", which prevents signals from reaching your app.
ENTRYPOINT ["python", "main.py"]
CMD ["--serve"]ENTRYPOINT defines the fixed executable, while CMD provides default arguments that users can override at "docker run".
Critical Docker Pitfalls & Precautions
- •If you override CMD when running "docker run image:tag custom_arg", only CMD is replaced; ENTRYPOINT remains active.
- •To completely override ENTRYPOINT, use "docker run --entrypoint /bin/sh image:tag".
ENTRYPOINT vs CMD Explained - Frequently Asked Questions
Common questions about container isolation, signal handling, and runtime behavior.
Use ENTRYPOINT ["node", "index.js"] or CMD ["node", "index.js"] in exec form (JSON array). Combining them allows passing default port or config flags.
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