Ubuntu一些old release version如11.04 ，9.10，源已经失效，安装一些命令或者包时候，无法获取到，网上搜索到的很多源都不能使用，几经周折找到了些可以用的源，具体操作步骤如下：
先备份源列表文件:
sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup
Ubuntu 11.04 old-releases源
deb http://old-releases.ubuntu.com/ubuntu/ natty main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ natty-security main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ natty-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ natty-proposed main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ natty-backports main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty-security main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty-updates main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty-proposed main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ natty-backports main restricted universe multiverse
更新源列表,使配置生效:
sudo apt-get update
