Linux拥有众多的发行版，每个发行版都有提供镜像，但是，有些镜像的下载速度参差不齐，偶尔会有更新失败的情况。

下面以修改 Ubuntu 软件源为中科大为例进行说明。

镜像地址：/

1、备份原配置文件

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

2、更改配置文件

编辑/etc/apt/sources.list文件, 将内容修改为：

Xenial(16.04)

deb /ubuntu/ xenial main restricted
deb /ubuntu/ xenial-updates main restricted
deb /ubuntu/ xenial universe
deb /ubuntu/ xenial-updates universe
deb /ubuntu/ xenial multiverse
deb /ubuntu/ xenial-updates multiverse
deb /ubuntu/ xenial-backports main restricted universe multiverse
deb /ubuntu/ xenial-security main restricted
deb /ubuntu/ xenial-security universe
deb /ubuntu/ xenial-security multiverse

Trusty(14.04)

deb /ubuntu/ trusty main restricted
deb /ubuntu/ trusty-updates main restricted
deb /ubuntu/ trusty universe
deb /ubuntu/ trusty-updates universe
deb /ubuntu/ trusty multiverse
deb /ubuntu/ trusty-updates multiverse
deb /ubuntu/ trusty-backports main restricted universe multiverse
deb /ubuntu/ trusty-security main restricted
deb /ubuntu/ trusty-security universe
deb /ubuntu/ trusty-security multiverse

deb /ubuntu/ precise main restricted
deb /ubuntu/ precise-updates main restricted
deb /ubuntu/ precise universe
deb /ubuntu/ precise-updates universe
deb /ubuntu/ precise multiverse
deb /ubuntu/ precise-updates multiverse
deb /ubuntu/ precise-backports main restricted universe multiverse
deb /ubuntu/ precise-security main restricted
deb /ubuntu/ precise-security universe
deb /ubuntu/ precise-security multiverse

# apt-get update