arm：
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-updates main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-backports main restricted universe multiverse