ubuntu 12.04 source.list 源更新

官方源：

 #deb cdrom:[Ubuntu 12.04 LTS _Precise Pangolin_ - Release i386 (20120423)]/ precise main restricted

 # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
 # newer versions of the distribution.
 deb http://us.archive.ubuntu.com/ubuntu/ precise main restricted
 deb-src http://us.archive.ubuntu.com/ubuntu/ precise main restricted

 ## Major bug fix updates produced after the final release of the
 ## distribution.
 deb http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted
 deb-src http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted

 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
 ## team. Also, please note that software in universe WILL NOT receive any
 ## review or updates from the Ubuntu security team.
 deb http://us.archive.ubuntu.com/ubuntu/ precise universe
 deb-src http://us.archive.ubuntu.com/ubuntu/ precise universe
 deb http://us.archive.ubuntu.com/ubuntu/ precise-updates universe
 deb-src http://us.archive.ubuntu.com/ubuntu/ precise-updates universe

 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
 ## team, and may not be under a free licence. Please satisfy yourself as to
 ## your rights to use the software. Also, please note that software in
 ## multiverse WILL NOT receive any review or updates from the Ubuntu
 ## security team.
 deb http://us.archive.ubuntu.com/ubuntu/ precise multiverse
 deb-src http://us.archive.ubuntu.com/ubuntu/ precise multiverse
 deb http://us.archive.ubuntu.com/ubuntu/ precise-updates multiverse
 deb-src http://us.archive.ubuntu.com/ubuntu/ precise-updates multiverse

 ## N.B. software from this repository may not have been tested as
 ## extensively as that contained in the main release, although it includes
 ## newer versions of some applications which may provide useful features.
 ## Also, please note that software in backports WILL NOT receive any review
 ## or updates from the Ubuntu security team.
 deb http://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse
 deb-src http://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse

 deb http://security.ubuntu.com/ubuntu precise-security main restricted
 deb-src http://security.ubuntu.com/ubuntu precise-security main restricted
 deb http://security.ubuntu.com/ubuntu precise-security universe
 deb-src http://security.ubuntu.com/ubuntu precise-security universe
 deb http://security.ubuntu.com/ubuntu precise-security multiverse
 deb-src http://security.ubuntu.com/ubuntu precise-security multiverse

 ## Uncomment the following two lines to add software from Canonical's
 ## 'partner' repository.
 ## This software is not part of Ubuntu, but is offered by Canonical and the
 ## respective vendors as a service to Ubuntu users.
 # deb http://archive.canonical.com/ubuntu precise partner
 # deb-src http://archive.canonical.com/ubuntu precise partner

 ## This software is not part of Ubuntu, but is offered by third-party
 ## developers who want to ship their latest software.
 deb http://extras.ubuntu.com/ubuntu precise main
 deb-src http://extras.ubuntu.com/ubuntu precise main

使用命令

 sudo gedit /etc/apt/sources.list

替换为中国本地源

 #163
 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
 #dianzi keji daxue
 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
 #beijing ligong daxue
 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

更新源到系统：

 sudo apt-get update
 sudo apt-get upgrade

搞定，OK，速度提升了几倍！