1、首先备份Ubuntu 8.04 的当前更新源列表
sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup （备份下当前的源列表，有备无患嘛）
2、修改更新源
sudo gedit /etc/apt/sources.list （打开Ubuntu 8.04源列表文件）
在最下面加入
deb hardy main restricted universe multiverse
deb hardy-security main restricted universe multiverse
deb hardy-updates main restricted universe multiverse
deb hardy-proposed main restricted universe multiverse
deb hardy-backports main restricted universe multiverse
deb-src hardy main restricted universe multiverse
deb-src hardy-security main restricted universe multiverse
deb-src hardy-updates main restricted universe multiverse
deb-src hardy-proposed main restricted universe multiverse
deb-src hardy-backports main restricted universe multiverse
3、通知Ubuntu 8.40 启用新的更新源
sudo apt-get update