Dockerfile中echo使用

Dockerfile 中的echo的使用方式和bash中的使用方式是有区别的
下面是一个 Dockerfile 通过echo的方式更换apt-get源和pip源

FROM python:3.5.8-stretch

# 更新缓存
RUN echo 'deb http://mirrors.aliyun.com/debian stretch main contrib non-free\n\
deb http://mirrors.aliyun.com/debian stretch-proposed-updates main contrib non-free\n\
deb http://mirrors.aliyun.com/debian stretch-updates main contrib non-free\n\
deb http://mirrors.aliyun.com/debian-security/ stretch/updates main non-free contrib\n'\
> /etc/apt/sources.list
RUN apt-get update

# 配置pip
RUN mkdir /root/.pip \
&& echo '[global]\n\
trusted-host = mirrors.aliyun.com\n\
index-url = https://mirrors.aliyun.com/pypi/simple\n'\
> /root/.pip/pip.conf

参考：Multiline Dockerfile syntax