Ubuntu 更改 apt-get 源 （转一叶云）
1. 首先备份系统apt-get源文件，以备将来换回来
sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup
2. 修改内容
#vim sources.list
清空并加入以下内容：
deb http://mirrors.163.com/ubuntu/ wily main restricted universe multiversedeb http://mirrors.163.com/ubuntu/ wily-security main restricted universe multiversedeb http://mirrors.163.com/ubuntu/ wily-updates main restricted universe multiversedeb http://mirrors.163.com/ubuntu/ wily-proposed main restricted universe multiversedeb http://mirrors.163.com/ubuntu/ wily-backports main restricted universe multiversedeb-src http://mirrors.163.com/ubuntu/ wily main restricted universe multiversedeb-src http://mirrors.163.com/ubuntu/ wily-security main restricted universe multiversedeb-src http://mirrors.163.com/ubuntu/ wily-updates main restricted universe multiversedeb-src http://mirrors.163.com/ubuntu/ wily-proposed main restricted universe multiversedeb-src http://mirrors.163.com/ubuntu/ wily-backports main restricted universe multiverse
这是国内的163镜像站点，速度非常快。运行sudo apt-get update命令，尝试可用。
