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 12.04源列表文件）
3、将下面的代码粘贴进去（“#”开头的那一行为注释，可以直接复制进文件中）
4、通知ubuntu启用新的更新源 sudo apt-get update
#网易 Ubuntu 12.04 源（速度很快） （本人再用）
#台湾源
deb precise main universe restricted multiverse
deb-src precise main universe restricted multiverse
deb precise-security universe main multiverse restricted
deb-src precise-security universe main multiverse restricted
deb precise-updates universe main multiverse restricted
deb-src precise-updates universe main multiverse restricted
#骨头源，骨头源是bones7456架设的一个Ubuntu源 ，提供ubuntu,deepin
deb precise main universe restricted multiverse
deb-src precise main universe restricted multiverse
deb precise-security universe main multiverse restricted
deb-src precise-security universe main multiverse restricted
deb precise-updates universe main multiverse restricted
deb precise-proposed universe main multiverse restricted
deb-src precise-proposed universe main multiverse restricted
deb precise-backports universe main multiverse restricted
deb-src precise-backports universe main multiverse restricted
deb-src precise-updates universe main multiverse restricted
#mirror.lupaworld.com的源，速度很快
deb precise main restricted universe multiverse
deb precise-security main restricted universe multiverse
deb precise-updates main restricted universe multiverse
deb precise-backports main restricted universe multiverse
deb precise main restricted universe multiverse
#ubuntu.cn99.com源（推荐）:
deb precise main restricted universe multiverse
deb precise-updates main restricted universe multiverse
deb precise-security main restricted universe multiverse
deb precise-backports main restricted universe multiverse
deb precise main restricted universe multiverse
#电子科技大学
deb precise main restricted universe multiverse
deb precise-backports main restricted universe multiverse
deb precise-proposed main restricted universe multiverse
deb precise-security main restricted universe multiverse
deb precise-updates main restricted universe multiverse
deb-src precise main restricted universe multiverse
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deb-src precise-proposed main restricted universe multiverse
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deb-src precise-updates main restricted universe multiverse
#中国科技大学
deb precise main restricted universe multiverse
deb precise-backports restricted universe multiverse
deb precise-proposed main restricted universe multiverse
deb precise-security main restricted universe multiverse
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deb-src precise main restricted universe multiverse
deb-src precise-backports main restricted universe multiverse
deb-src precise-proposed main restricted universe multiverse
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deb-src precise-updates main restricted universe multiverse
#北京理工大学
deb precise main multiverse restricted universe
deb precise-backports main multiverse restricted universe
deb precise-proposed main multiverse restricted universe
deb precise-security main multiverse restricted universe
deb precise-updates main multiverse restricted universe
deb-src precise main multiverse restricted universe
deb-src precise-backports main multiverse restricted universe
deb-src precise-proposed main multiverse restricted universe
deb-src precise-security main multiverse restricted universe
deb-src precise-updates main multiverse restricted universe
#兰州大学
deb ftp://mirror.lzu.edu.cn/ubuntu/ precise main multiverse restricted universe
deb ftp://mirror.lzu.edu.cn/ubuntu/ precise-backports main multiverse restricted universe
deb ftp://mirror.lzu.edu.cn/ubuntu/ precise-proposed main multiverse restricted universe
deb ftp://mirror.lzu.edu.cn/ubuntu/ precise-security main multiverse restricted universe
deb ftp://mirror.lzu.edu.cn/ubuntu/ precise-updates main multiverse restricted universe
deb ftp://mirror.lzu.edu.cn/ubuntu-cn/ precise main multiverse restricted universe
#上海交通大学
deb precise main multiverse restricted universe
deb precise-backports main multiverse restricted universe
deb precise-proposed main multiverse restricted universe
deb precise-security main multiverse restricted universe
deb precise-updates main multiverse restricted universe
deb precise main multiverse restricted universe
deb-src precise main multiverse restricted universe
deb-src precise-backports main multiverse restricted universe
deb-src precise-proposed main multiverse restricted universe
deb-src precise-security main multiverse restricted universe
deb-src precise-updates main multiverse restricted universe