ubuntu12.04 precise更新源

1. 首先備份Ubuntu12.04源列表

   sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup （備份下當前的源列表）

2. 修改更新源

   sudo gedit /etc/apt/sources.list （打開Ubuntu 12.04源列表文件）

3. 把裏面的列表替換成下面的列表

   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

4. 更新源

   sudo apt-get update