树莓派更改更新源

1、先用pi用户登录树莓派

          账号：pi

          密码：raspberry

2、然后修改超级用户root密码

         sudo passwd root

3、切换到root用户

          su - root

4、修改 /etc/apt/sources.list

         sudo nano /etc/apt/sources.list

         原文deb http://mirrordirector.raspbian.org/raspbian/ stretch main contrib non-free rp， 加#注释掉

         加入如下阿里源，deb http://mirrors.aliyun.com/raspbian/raspbian/ stretch main contrib non-free rpi

5、修改/etc/apt/sources.list.d/raspi.list

       sudo nano /etc/apt/sources.list.d/raspi.list

      原文deb http://archive.raspberrypi.org/debian/ stretch main ui， 加#

      加入如下科大源：deb http://mirrors.ustc.edu.cn/archive.raspberrypi.org/debian/ stretch main ui

6、更新系统和软件

        sudo apt-get update && apt-get upgrade