http://mirrors.cn99.com/.help/ubuntu.html
以Precise(12.04)为例, 编辑/etc/apt/sources.list文件, 在文件最前面添加以下条目(操作前请做好相应备份)
deb http://mirrors.163.com/ubuntu/ precise main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ precise-security main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ precise-updates main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ precise-proposed main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ precise main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ precise-security main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ precise-updates main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ precise-proposed main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse
或者下载相应版本的sources.list, 覆盖/etc/apt/sources.list即可(操作前请做好相应备份)