sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup //（备份下当前的源列表）
2、修改更新源
sudo gedit /etc/apt/sources.list
3、把里面的列表替换成下面的列表
3.1 163源
deb http://mirrors.163.com/ubuntu/ precise main restricted deb-src http://mirrors.163.com/ubuntu/ precise main restricted deb http://mirrors.163.com/ubuntu/ precise-updates main restricted deb-src http://mirrors.163.com/ubuntu/ precise-updates main restricted deb http://mirrors.163.com/ubuntu/ precise universe deb-src http://mirrors.163.com/ubuntu/ precise universe deb http://mirrors.163.com/ubuntu/ precise-updates universe deb-src http://mirrors.163.com/ubuntu/ precise-updates universe deb http://mirrors.163.com/ubuntu/ precise multiverse deb-src http://mirrors.163.com/ubuntu/ precise multiverse deb http://mirrors.163.com/ubuntu/ precise-updates multiverse deb-src http://mirrors.163.com/ubuntu/ precise-updates multiverse deb http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ precise-security main restricted deb-src http://mirrors.163.com/ubuntu/ precise-security main restricted deb http://mirrors.163.com/ubuntu/ precise-security universe deb-src http://mirrors.163.com/ubuntu/ precise-security universe deb http://mirrors.163.com/ubuntu/ precise-security multiverse deb-src http://mirrors.163.com/ubuntu/ precise-security multiverse deb http://extras.ubuntu.com/ubuntu precise main deb-src http://extras.ubuntu.com/ubuntu precise main
或
deb ftp://mirrors.ustc.edu.cn/linuxmint/ maya main upstream import deb http://mirrors.163.com/ubuntu/ precise main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ precise-updates main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ precise-security main restricted universe multiverse deb http://archive.canonical.com/ubuntu/ precise partner deb http://packages.medibuntu.org/ precise free non-free
3.2 sohu源
deb http://mirrors.sohu.com/ubuntu/ precise main restricted deb-src http://mirrors.sohu.com/ubuntu/ precise main restricted deb http://mirrors.sohu.com/ubuntu/ precise-updates main restricted deb-src http://mirrors.sohu.com/ubuntu/ precise-updates main restricted deb http://mirrors.sohu.com/ubuntu/ precise universe deb-src http://mirrors.sohu.com/ubuntu/ precise universe deb http://mirrors.sohu.com/ubuntu/ precise-updates universe deb-src http://mirrors.sohu.com/ubuntu/ precise-updates universe deb http://mirrors.sohu.com/ubuntu/ precise multiverse deb-src http://mirrors.sohu.com/ubuntu/ precise multiverse deb http://mirrors.sohu.com/ubuntu/ precise-updates multiverse deb-src http://mirrors.sohu.com/ubuntu/ precise-updates multiverse deb http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse deb-src http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse deb http://mirrors.sohu.com/ubuntu/ precise-security main restricted deb-src http://mirrors.sohu.com/ubuntu/ precise-security main restricted deb http://mirrors.sohu.com/ubuntu/ precise-security universe deb-src http://mirrors.sohu.com/ubuntu/ precise-security universe deb http://mirrors.sohu.com/ubuntu/ precise-security multiverse deb-src http://mirrors.sohu.com/ubuntu/ precise-security multiverse deb http://extras.ubuntu.com/ubuntu precise main deb-src http://extras.ubuntu.com/ubuntu precise main
3.3 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
3.4 教育网源
如果你是在校学生，可以使用校园网/教育网，更新速度更快。
#3.4.1 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
#3.4.2 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
#3.4.3 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
4、更新源
sudo apt-get update