1、首先备份Ubuntu 12.04源列表 

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

#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