在进行linux软件包下载更新时，报错
apt-get update连接不上
进入 vi /etc/apt/sources.list
将网址修改为如下之一即可。
163源
deb http://mirrors.163.com/debian/ jessie main non-free contrib
deb http://mirrors.163.com/debian/ jessie-updates main non-free contrib
deb http://mirrors.163.com/debian/ jessie-backports main non-free contrib
deb-src http://mirrors.163.com/debian/ jessie main non-free contrib
deb-src http://mirrors.163.com/debian/ jessie-updates main non-free contrib
deb-src http://mirrors.163.com/debian/ jessie-backports main non-free contrib
deb http://mirrors.163.com/debian-security/ jessie/updates main non-free contrib
deb-src http://mirrors.163.com/debian-security/ jessie/updates main non-free contrib
中科大源
deb http://mirrors.ustc.edu.cn/debian jessie main contrib non-free
deb-src http://mirrors.ustc.edu.cn/debian jessie main contrib non-free
deb http://mirrors.ustc.edu.cn/debian jessie-proposed-updates main contrib non-free
deb-src http://mirrors.ustc.edu.cn/debian jessie-proposed-updates main contrib non-free
deb http://mirrors.ustc.edu.cn/debian jessie-updates main contrib non-free
deb-src http://mirrors.ustc.edu.cn/debian jessie-updates main contrib non-free