1、開啟配置更新URL的配置檔案

      在終端輸入命令： gedit /etc/apt/sources.list

2、刪除sources.list檔案的內容，把下列的更新源URL複製到檔案中

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

precise-updates main restricted universe multiverse
      deb http://archive.ubuntu.com/ubuntu/ precise-proposed main restricted universe multiverse
      deb http://archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse
      deb-src http://archive.ubuntu.com/ubuntu/ precise main restricted universe multiverse
      deb-src

http://archive.ubuntu.com/ubuntu/ precise-security main restricted universe multiverse
      deb-src http://archive.ubuntu.com/ubuntu/ precise-updates main restricted universe multiverse
      deb-src http://archive.ubuntu.com/ubuntu/ precise-proposed main restricted universe multiverse
      deb-src http://archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse

3、儲存關閉檔案

4、在終端輸入命令： sudo apt-get update 更新(注：必須執行這個命令，否則更新源不啟作用)