Question 178520 in Docker Question posted in
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Can multiple CMDs be passed to Dockerfile as ARGs?

I’m trying to pass 2 commands to Dockerfile to be executed one after another, but have had no luck since:
Dockerfile:

FROM alpine
ARG COMMAND
ENV COMMAND=${COMMAND}
CMD "${COMMAND}"

docker.compose.yml:

version: '3.7'

services:
  check_requirements:
    image: my_test_image
    build:
      args:
        COMMAND: "echo 1; echo 2"
      context: .
      dockerfile: Dockerfile

when I run docker compose build and then docker compose run test (or docker container run -it my_test_image) I get:

/bin/sh: echo 1; echo 2: not found

If I substitute last line of Dockerfile with:

CMD ["sh", "-c", "${COMMAND}"]

I get

1; echo 2

Expected:
on CMD Docker runs echo 1 and then echo 2

Is what I am trying to achieve possible?

Tags:

2

Answers


  1. 0

    I’m trying to pass 2 commands a script to Dockerfile to be executed

    Sure, then write the script content to a file and execute.

    ARG COMMAND
ENV COMMAND=${COMMAND}
RUN printenv "$COMMAND" > /script.sh
CMD ["sh", "/script.sh"]

    Or you can call eval to evaluate the content of an environment variable.

    ARG COMMAND
ENV COMMAND=${COMMAND}
CMD ["sh", "-c", "eval "$COMMAND""]
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  2. 0

    You can just override the command when you run the container. You do not need to try to marshal it through an environment variable or build ARG.

    version: '3.8'
services:
  check_requirements:
    build: .
    command: sh -c 'echo 1; echo 2'

    I’d suggest making the Dockerfile CMD be the "default" thing you expect a container to do. This is one of a couple of things I would not make parameterized; just declare a fixed CMD and allow it to be overridden when you run the container. (One specific example that comes to mind is a Python application where the default CMD runs a Django application but you can override Compose command: to run a Celery worker from the same code base.)

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