先备份/etc/apt/sources.list
然后修改：
sudo gedit /etc/apt/sources.list（或者使用你喜欢的编辑器）

增加下面的行(hardy版，即8.04):
代码:
deb http://mirror.lupaworld.com/ubuntu hardy main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu hardy-security main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu hardy-updates main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu hardy-backports main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu hardy main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu hardy-security main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu hardy-updates main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu hardy-backports main restricted universe multiverse

增加下面的行(gutsy版，即7.10):
代码:
deb http://mirror.lupaworld.com/ubuntu gutsy main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu gutsy-security main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu gutsy-updates main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu gutsy-backports main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu gutsy main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu gutsy-security main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu gutsy-updates main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu gutsy-backports main restricted universe multiverse

增加下面的行(feisty版，即7.04):
代码:
deb http://mirror.lupaworld.com/ubuntu feisty main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu feisty-security main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu feisty-updates main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu feisty-backports main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu/ubuntu-cn feisty main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu feisty main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu feisty-security main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu feisty-updates main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu feisty-backports main restricted universe multiverse

增加下面的行(dapper版，即6.06):
代码:
deb http://mirror.lupaworld.com/ubuntu dapper main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu dapper-security main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu dapper-updates main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu dapper-backports main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu/ubuntu-cn dapper main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu dapper main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu dapper-security main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu dapper-updates main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu dapper-backports main restricted universe multiverse

注：这个镜像是完全镜像。并且包含了光盘下载的整个镜像！
光盘下载： http://mirror.lupaworld.com/ubuntu/releases/