dockerfile 官方源改变成国内源

RUN mv /etc/apt/sources.list /etc/apt/sources.list.bak && \
    echo "deb http://mirrors.163.com/debian/ stretch main non-free contrib" >/etc/apt/sources.list && \
    echo "deb http://mirrors.163.com/debian/ stretch-updates main non-free contrib" >>/etc/apt/sources.list && \
    echo "deb http://mirrors.163.com/debian/ stretch-backports main non-free contrib" >>/etc/apt/sources.list && \
    echo "deb-src http://mirrors.163.com/debian/ stretch main non-free contrib" >>/etc/apt/sources.list && \
    echo "deb-src http://mirrors.163.com/debian/ stretch-updates main non-free contrib" >>/etc/apt/sources.list && \
    echo "deb-src http://mirrors.163.com/debian/ stretch-backports main non-free contrib" >>/etc/apt/sources.list && \
    echo "deb http://mirrors.163.com/debian-security/ stretch/updates main non-free contrib" >>/etc/apt/sources.list && \
    echo "deb-src http://mirrors.163.com/debian-security/ stretch/updates main non-free contrib" >>/etc/apt/sources.list