CMD指令中是否允许Docker ARG [英] Is Docker ARG allowed within CMD instruction

问题描述

我有一个Dockerfile，在 CMD 指令中使用了 ARG ：

I have a Dockerfile where an ARG is used in the CMD instruction:

ARG MASTER_NAME
CMD spark-submit --deploy-mode client --master ${MASTER_URL}

arg通过docker-compose传递：

The arg is passed via docker-compose:

  spark:
    build:
      context: spark
      args:
        - MASTER_URL=spark://master:7077

但是， ARG 似乎没有为 CMD 。在我 docker-compose up 之后。

However, the ARG does not seem to get expanded for CMD. After I docker-compose up.

这里是检查显示的内容：

Here's what inspect shows:

docker inspect  -f "{{.Name}} {{.Config.Cmd}}" $(docker ps -a -q)
/spark {[/bin/sh -c spark-submit --deploy-mode client --master ${MASTER_URL}]}

推荐答案

问题在于 args 仅可在构建时使用，而 CMD 在运行时执行。我想现在唯一实现目标的方法是在Dockerfile中使用 MASTER_NAME 值设置环境变量。

The thing is that args only can be used at build time, and the CMD is executing at run time. I guess that the only approach now to achieve what you want is setting an environment variable in the Dockerfile with the MASTER_NAME value.

ARG MASTER_NAME
ENV MASTER_NAME ${MASTER_NAME}
CMD spark-submit --deploy-mode client --master ${MASTER_NAME}

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