MultipleInstructionsDisallowed
Table of contents
Output
Multiple CMD instructions should not be used in the same stage because only the last one will be used
Description
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
.
Examples
❌ 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