更换核心板数据源

deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse