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Multiple CMD instructions should not be used in the same stage because only the last one will be used


If you have multiple CMD, HEALTHCHECK, or ENTRYPOINT instructions in your Dockerfile, only the last occurrence is used. An image can only ever have one CMD, HEALTHCHECK, and ENTRYPOINT.


❌ Bad: Duplicate instructions.

FROM alpine
CMD echo "Hello, Norway!"
CMD echo "Hello, Sweden!"
# Only "Hello, Sweden!" will be printed

✅ Good: only one CMD instruction.

FROM alpine
CMD echo "Hello, Norway!"; echo "Hello, Sweden!"

You can have both a regular, top-level CMD and a separate CMD for a HEALTHCHECK instruction.

✅ Good: only one top-level CMD instruction.

FROM python:alpine
RUN apk add curl
HEALTHCHECK --interval=1s --timeout=3s \
  CMD curl -f http://localhost:8080 || exit 1
CMD python -m http.server 8080