更换阿里云源，启用root

sudo nano /etc/apt/sources.list

注释掉原来的源后，添加

deb http://mirrors.aliyun.com/raspbian/raspbian/jessie main non-free contrib

deb-src http://mirrors.aliyun.com/raspbian/raspbian/jessie main non-free contrib

然后启用root：

sudo passwd root

根据提示设置密码，切换到root管理员

su root 

更新

sudo apt-get update && apt-get upgrade -y