Docker and CI/CD · Junior · Question 5 of 75

What is the difference between `RUN` and `CMD`?

✓Correct answer: RUN executes at build time; CMD sets what runs at container start
2RUN is for Linux images, while CMD is for Windows images
3RUN starts the app in the background; CMD starts it in the foreground

Explanation

RUN npm ci bakes the result into an image layer. CMD ["node", "server.js"] is only metadata: the default command when a container starts.

Further reading

Docker Docs: Dockerfile reference ↗

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