1、先备份好系统自带的源列表

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

2、修改源列表文件

vi /etc/apt/sources.list

删除系统自带的源列表【sources.list】里的内容，再将下列源复制粘贴到源列表文件后保存。

注意：要添加一整套源，不要只在源列表中添加1条源

例如：添加阿里源到sources.list中

163源：

deb http://mirrors.163.com/ubuntu/ precise main restricted universe multiverse

deb http://mirrors.163.com/ubuntu/ precise-security main restricted universe multiverse

deb http://mirrors.163.com/ubuntu/ precise-updates main restricted universe multiverse

deb http://mirrors.163.com/ubuntu/ precise-proposed main restricted universe multiverse

deb http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse

deb-src http://mirrors.163.com/ubuntu/ precise main restricted universe multiverse

deb-src http://mirrors.163.com/ubuntu/ precise-security main restricted universe multiverse

deb-src http://mirrors.163.com/ubuntu/ precise-updates main restricted universe multiverse

deb-src http://mirrors.163.com/ubuntu/ precise-proposed main restricted universe multiverse

deb-src http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse

阿里源：

deb http://mirrors.aliyun.com/ubuntu/ precise main restricted universe multiverse

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

deb http://mirrors.aliyun.com/ubuntu/ precise-updates main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ precise-proposed main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ precise-backports main restricted universe multiverse

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

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

deb-src http://mirrors.aliyun.com/ubuntu/ precise-updates main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ precise-proposed main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ precise-backports main restricted universe multiverse

3、刷新源列表

sudo apt-get update

刷新完成会显示如下图所示，由于使用的是阿里源，所以下图显示的是阿里源列表信息

使用官方源可能会在更新包时，存在更新缓慢的情况，所以建议使用163或阿里源，国内下载更新首选。