Dockerfile:在单行中设置多个环境变量 [英] Dockerfile: Setting multiple environment variables in single line

问题描述

我的印象是可以将环境变量设置在一行中，以尽量减少中间图像.

I was under the impression that environmental variables could be set on a single line as follows so as to minimize intermediary images.

FROM alpine:3.6
ENV RUBY_MAJOR 2.4 
    RUBY_VERSION 2.4.1 
    RUBY_DOWNLOAD_SHA256 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654 
    RUBYGEMS_VERSION 2.6.12 
    BUNDLER_VERSION 1.15.3

但是，基于此代码段运行容器并调用 # set |grep RU 我看到变量没有单独分配，而是组合成一个字符串.

However, running a container based off of this snippet and calling # set |grep RU I see that the variables are not being assigned separately, but are combined into a single string.

RUBY_MAJOR='2.4     RUBY_VERSION 2.4.1     RUBY_DOWNLOAD_SHA256 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654     RUBYGEMS_VERSION 2.6.12     BUNDLER_VERSION 1.15.3'

但是，如果我如下明确设置每个变量，我会得到预期的输出，并且在调用变量时没有错误.

However, if I explicitly set each variable as below, I get the expected output and there are no errors when calling the variables.

ENV RUBY_MAJOR 2.4
ENV RUBY_VERSION 2.4.1
ENV RUBY_DOWNLOAD_SHA256 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654
ENV RUBYGEMS_VERSION 2.6.12
ENV BUNDLER_VERSION 1.15.3

问题:是否可以将环境变量的设置组合在一行中?如果是这样，我会怎么做?这是一个好习惯吗?

Question: Is it is possible to combine the setting of environment variables on a single line? If so, how would I do it? And is it a good practice?

推荐答案

指定环境有两种格式.如果你需要单个变量，那么你下面的格式

There are two formats for specifying environments. If you need single variable then you below format

ENV X Y

这会将 X 分配为 Y

ENV X Y Z

这会将 X 分配为 Y Z

如果您需要分配多个环境变量，则使用其他格式

If you need to assign multiple environment variables then you use the other format

ENV X=Y Z=A

这会将 X 指定为 Y 并将 Z 指定为 A.所以你的 Dockerfile 应该是

This will assign X as Y and Z as A. So your Dockerfile should be

FROM alpine:3.6
ENV RUBY_MAJOR=2.4 
    RUBY_VERSION=2.4.1 
    RUBY_DOWNLOAD_SHA256=4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654 
    RUBYGEMS_VERSION=2.6.12 
    BUNDLER_VERSION=1.15.3

RUN env

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