每个 Dockerfile RUN 步骤运行一个新容器和一个新 shell.如果您尝试在一个 shell 中设置环境变量，稍后它将不可见.例如，您可以试验这个 Dockerfile:

Each Dockerfile RUN step runs a new container and a new shell. If you try to set an environment variable in one shell, it will not be visible later on. For example, you might experiment with this Dockerfile:

FROM busybox
ENV FOO=foo1
RUN export FOO=foo2
RUN export BAR=bar
CMD echo FOO is $FOO, BAR is $BAR
# Prints "FOO is foo1, BAR is "

对此有三个很好的解决方案.按照从最简单/***到最难/最复杂的顺序:

There are three good solutions to this. In order from easiest/best to hardest/most complex:

1. 完全避免需要环境变量.将软件安装到系统"位置，例如/usr；无论如何，它将被隔离在 Docker 映像中.(不要使用额外的隔离工具，比如 Python 虚拟环境，或者像 nvm 或 rvm 这样的版本管理器；只需安装你需要的特定东西.)

1. Avoid needing the environment variables at all. Install software into "system" locations like /usr; it will be isolated inside the Docker image anyways. (Don’t use an additional isolation tool like Python virtual environments, or a version manager like nvm or rvm; just install the specific thing you need.)

使用ENV.这将工作:

FROM busybox
ENV FOO=foo2
ENV BAR=bar
CMD echo FOO is $FOO, BAR is $BAR
# Prints "FOO is foo2, BAR is bar"

#!/bin/sh
# Read in the file of environment settings
. /opt/wherever/env
# Then run the CMD
exec "$@"

FROM busybox
WORKDIR /app
COPY entrypoint.sh .
COPY more_stuff .
ENTRYPOINT ["/app/entrypoint.sh"]
CMD ["/app/more_stuff/my_app"]