sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak #备份本机原源文件。

sudo vim /etc/apt/sources.list #修改源文件，以下内容替换原内容。

==[sources.list]=============================

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

deb http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse

=======================================

sudo apt-get update #更新列表。