Docker 运行 exec 形式的命令不起作用

Question

我正在构建一个基于 Alpine 的 docker 图像。

FROM alpine

RUN apk update \
    && apk add lighttpd \
    && rm -rf /var/cache/apk/*

ENV COLOR red

COPY ./index.html /var/www/localhost/htdocs

RUN /bin/ash -c 'echo abcd'
#working
RUN /bin/ash -c "echo $COLOR; sed -i -e 's/red/$COLOR/g' /var/www/localhost/htdocs/index.html; cat /var/www/localhost/htdocs/index.html;"
#not working
# RUN ["sh", "-c", "echo $COLOR; sed -i -e 's/red/$COLOR/g' /var/www/localhost/htdocs/index.html; cat /var/www/localhost/htdocs/index.html;"]

CMD ["lighttpd","-D","-f","/etc/lighttpd/lighttpd.conf"]

当我运行以 shell 形式工作时它工作正常，但是当我运行以 exec 形式它给出

/bin/sh: [sh,: not found

我尝试使用 bin/sh、sh、bin/ash、ash。所有人都犯同样的错误。

Answer 1

我已经使用 Docker 几年了，我不知道（直到你的问题）有 shell|RUN 的执行表格 ;-)

问题是您的命令包含环境变量 ($COLOR)，并且 exec 形式没有替代|求值。

参见：

https://docs.docker.com/engine/reference/builder/#run

“与 shell 形式不同，exec 形式不调用命令 shell。这意味着正常的 shell 处理不会发生”

Answer 2

Shell负责扩展变量，但只有双引号内的变量才会被扩展。

你的错误来自于$COLOR之前的错误\，其实你从shell取值是没有意义的，正确的做法是：[=15] =]

RUN ["sh", "-c", "echo $COLOR; sed -i -e \"s/red/$COLOR/g\" /var/www/localhost/htdocs/index.html; cat /var/www/localhost/htdocs/index.html;"]

显示效果的最小示例，仅供参考：

Dockerfile:

FROM alpine
ENV COLOR rednew
RUN echo "red" > /tmp/index.html
RUN ["sh", "-c", "sed -i -e \"s/red/$COLOR/g\" /tmp/index.html; cat /tmp/index.html;"]

结果：

$ docker build -t abc:1 . --no-cache                                                                                              
Sending build context to Docker daemon  5.632kB
Step 1/4 : FROM alpine
 ---> 28f6e2705743
Step 2/4 : ENV COLOR rednew
 ---> Running in 05c43146fab0
Removing intermediate container 05c43146fab0
 ---> 28ea1434e626
Step 3/4 : RUN echo "red" > /tmp/index.html
 ---> Running in 2c8fbbc5fd10
Removing intermediate container 2c8fbbc5fd10
 ---> f884892ad8c4
Step 4/4 : RUN ["sh", "-c", "sed -i -e \"s/red/$COLOR/g\" /tmp/index.html; cat /tmp/index.html;"]
 ---> Running in 6930b3d03438
rednew
Removing intermediate container 6930b3d03438
 ---> b770475672cc
Successfully built b770475672cc
Successfully tagged abc:1

Docker 运行 exec 形式的命令不起作用

Docker RUN command in exec form not working

docker

alpine