很多教程给的url都没有经过测试，两个需要修改的文件及写入的文本如下：
# /etc/apt/sources.list deb http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ buster main contrib non-free rpi deb-src http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ buster main contrib non-free rpi # /etc/apt/sources.list.d/raspi.list deb https://mirrors.tuna.tsinghua.edu.cn/raspberrypi/ buster main