arm ubuntu souce :

清华源：
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-updates main restricted universe multiverse  
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-updates main restricted universe multiverse   
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-security main restricted universe multiverse   
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-security main restricted universe multiverse   
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-backports main restricted universe multiverse   
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-backports main restricted universe multiverse   
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial main universe restricted   
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial main universe restricted 


科大的源：

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

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

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