树莓派使用科大镜像源

修改/etc/apt/sources.list
将mirrordirector.raspbian.org替换为mirrors.ustc.edu.cn/raspbian/

修改/etc/apt/raspi.list
将archive.raspberrypi.org替换为mirrors.ustc.edu.cn/archive.raspberrypi.org

清华镜像源
https://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian