问题描述
我有一个像这样的Dockerfile:
I have a Dockerfile starts like this:
FROM ubuntu:16.04
WORKDIR /some/path
COPY . .
ENV PYTHONUSERBASE=$PWD/pyenv PATH=$PWD/pyenv/bin:$PATH
RUN echo "PWD is: $PWD"
RUN echo "PYENV is: $PYTHONUSERBASE"
我发现运行 docker build 时未设置 $ PWD (或 $ {PWD} )，作为比较， $ PATH 已正确展开.
I found $PWD (or ${PWD}) was not set when I run docker build, as a comparison, $PATH was correctly expanded.
此外， RUN 中的 $ PWD 没问题(在这种情况下，它会打印/some/path )
Moreover, $PWD in RUN has no problem (It prints /some/path in this case)
因此给定Dockerfile的输出为:
So the output of the given Dockerfile would be:
PWD is: /some/path
PYENV is: /pyenv
有人可以告诉我为什么 $ PWD 如此特别吗?我想这可能与 WORKDIR 的行为有关，但我对此一无所知.
Could somebody tell me why $PWD is so special? I guess it may be related to the behaviour of WORKDIR but I have no clue about that.
推荐答案
PWD是在shell内设置的特殊变量.当docker RUN时，它以 sh -c'something'的形式执行此操作，从ENV指令传递预定义的环境变量，其中PWD不在该列表中(请参见 docker检查< image-id> ).
PWD is an special variable that is set inside a shell. When docker RUN something it does that with this form sh -c 'something', passing the pre-defined environment variables from ENV instructions, where PWD is not in that list (see it with docker inspect <image-id>).
ENV指令不会启动外壳程序.只需在图像元数据中添加或更新环境变量的当前列表即可.
ENV instructions does not launch a shell. Simply add or update the current list of env vars in the image metadata.
我将这样编写您的Dockerfile:
I would write your Dockerfile as this:
FROM ubuntu:16.04
ENV APP_PATH=/some/path
WORKDIR $APP_PATH
COPY . .
ENV PYTHONUSERBASE=$APP_PATH/pyenv PATH=$APP_PATH/pyenv/bin:$PATH
RUN echo "PWD is: $PWD"
RUN echo "PYENV is: $PYTHONUSERBASE"
文档中的其他信息:
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