1) 备份源列表

sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup

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

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