1、修改更新源
sudo vi /etc/apt/sources.list （打开Ubuntu 12.04源列表文件）
2、清空sources.list, 将下面的代码粘贴进去
#台湾源 deb http://tw.archive.ubuntu.com/ubuntu/ precise main universe restricted multiverse deb-src http://tw.archive.ubuntu.com/ubuntu/ precise main universe restricted multiverse deb http://tw.archive.ubuntu.com/ubuntu/ precise-security universe main multiverse restricted deb-src http://tw.archive.ubuntu.com/ubuntu/ precise-security universe main multiverse restricted deb http://tw.archive.ubuntu.com/ubuntu/ precise-updates universe main multiverse restricted deb-src http://tw.archive.ubuntu.com/ubuntu/ precise-updates universe main multiverse restricted #网易 Ubuntu 11.10 源（速度很快） deb http://mirrors.163.com/ubuntu/ precise main universe restricted multiverse deb-src http://mirrors.163.com/ubuntu/ precise main universe restricted multiverse deb http://mirrors.163.com/ubuntu/ precise-security universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ precise-security universe main multiverse restricted deb http://mirrors.163.com/ubuntu/ precise-updates universe main multiverse restricted deb http://mirrors.163.com/ubuntu/ precise-proposed universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ precise-proposed universe main multiverse restricted deb http://mirrors.163.com/ubuntu/ precise-backports universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ precise-backports universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ 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 http://ubuntu.srt.cn/ubuntu/ precise main universe restricted multiverse deb-src http://ubuntu.srt.cn/ubuntu/ precise main universe restricted multiverse deb http://ubuntu.srt.cn/ubuntu/ precise-security universe main multiverse restricted deb-src http://ubuntu.srt.cn/ubuntu/ precise-security universe main multiverse restricted deb http://ubuntu.srt.cn/ubuntu/ precise-updates universe main multiverse restricted deb http://ubuntu.srt.cn/ubuntu/ precise-proposed universe main multiverse restricted deb-src http://ubuntu.srt.cn/ubuntu/ precise-proposed universe main multiverse restricted deb http://ubuntu.srt.cn/ubuntu/ precise-backports universe main multiverse restricted deb-src http://ubuntu.srt.cn/ubuntu/ precise-backports universe main multiverse restricted deb-src http://ubuntu.srt.cn/ubuntu/ precise-updates universe main multiverse restricted #mirror.lupaworld.com的源，速度很快 deb http://mirror.lupaworld.com/ubuntu/archive/ precise main restricted universe multiverse deb http://mirror.lupaworld.com/ubuntu/archive/ precise-security main restricted universe multiverse deb http://mirror.lupaworld.com/ubuntu/archive/ precise-updates main restricted universe multiverse deb http://mirror.lupaworld.com/ubuntu/archive/ precise-backports main restricted universe multiverse deb http://mirror.lupaworld.com/ubuntu/ubuntu-cn/ precise main restricted universe multiverse #ubuntu.cn99.com源（推荐）: deb http://ubuntu.cn99.com/ubuntu/ precise main restricted universe multiverse deb http://ubuntu.cn99.com/ubuntu/ precise-updates main restricted universe multiverse deb http://ubuntu.cn99.com/ubuntu/ precise-security main restricted universe multiverse deb http://ubuntu.cn99.com/ubuntu/ precise-backports main restricted universe multiverse deb http://ubuntu.cn99.com/ubuntu-cn/ precise main restricted universe multiverse #电子科技大学 deb http://ubuntu.uestc.edu.cn/ubuntu/ precise main restricted universe multiverse deb http://ubuntu.uestc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse deb http://ubuntu.uestc.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse deb http://ubuntu.uestc.edu.cn/ubuntu/ precise-security main restricted universe multiverse deb http://ubuntu.uestc.edu.cn/ubuntu/ precise-updates main restricted universe multiverse deb-src http://ubuntu.uestc.edu.cn/ubuntu/ precise main restricted universe multiverse deb-src http://ubuntu.uestc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse deb-src http://ubuntu.uestc.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse deb-src http://ubuntu.uestc.edu.cn/ubuntu/ precise-security main restricted universe multiverse deb-src http://ubuntu.uestc.edu.cn/ubuntu/ precise-updates main restricted universe multiverse #中国科技大学 deb http://debian.ustc.edu.cn/ubuntu/ precise main restricted universe multiverse deb http://debian.ustc.edu.cn/ubuntu/ precise-backports restricted universe multiverse deb http://debian.ustc.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse deb http://debian.ustc.edu.cn/ubuntu/ precise-security main restricted universe multiverse deb http://debian.ustc.edu.cn/ubuntu/ precise-updates main restricted universe multiverse deb-src http://debian.ustc.edu.cn/ubuntu/ precise main restricted universe multiverse deb-src http://debian.ustc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse deb-src http://debian.ustc.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse deb-src http://debian.ustc.edu.cn/ubuntu/ precise-security main restricted universe multiverse deb-src http://debian.ustc.edu.cn/ubuntu/ precise-updates main restricted universe multiverse #北京理工大学 deb http://mirror.bjtu.edu.cn/ubuntu/ precise main multiverse restricted universe deb http://mirror.bjtu.edu.cn/ubuntu/ precise-backports main multiverse restricted universe deb http://mirror.bjtu.edu.cn/ubuntu/ precise-proposed main multiverse restricted universe deb http://mirror.bjtu.edu.cn/ubuntu/ precise-security main multiverse restricted universe deb http://mirror.bjtu.edu.cn/ubuntu/ precise-updates main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/ubuntu/ precise main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/ubuntu/ precise-backports main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/ubuntu/ precise-proposed main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/ubuntu/ precise-security main multiverse restricted universe deb-src http://mirror.bjtu.edu.cn/ubuntu/ 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 http://ftp.sjtu.edu.cn/ubuntu/ precise main multiverse restricted universe deb http://ftp.sjtu.edu.cn/ubuntu/ precise-backports main multiverse restricted universe deb http://ftp.sjtu.edu.cn/ubuntu/ precise-proposed main multiverse restricted universe deb http://ftp.sjtu.edu.cn/ubuntu/ precise-security main multiverse restricted universe deb http://ftp.sjtu.edu.cn/ubuntu/ precise-updates main multiverse restricted universe deb http://ftp.sjtu.edu.cn/ubuntu-cn/ precise main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/ubuntu/ precise main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/ubuntu/ precise-backports main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/ubuntu/ precise-proposed main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/ubuntu/ precise-security main multiverse restricted universe deb-src http://ftp.sjtu.edu.cn/ubuntu/ precise-updates main multiverse restricted universe
3、通知ubuntu启用新的更新源
sudo apt-get update