$ sudo nano /etc/apt/sources.listdeb http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ stretch main contrib non-free rpideb-src http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ stretch main contrib non-free rpideb http://mirrors.neusoft.edu.cn/raspbian/raspbian/ stretch main contrib non-free rpideb-src http://mirrors.neusoft.edu.cn/raspbian/raspbian/ stretch main contrib non-free rpi