大伟哥在Ubuntu Server 16.04更新系统软件包一文中提到过，如果你在国内使用Ubuntu Linux系统，可以考虑把Ubuntu的软件源换成国内的，这样下载安装软件就会比较快。
什么是Ubuntu的软件源？
我们在使用Debian或者Ubuntu的apt-get工具来安装需要的软件时，其实就是从服务器获取需要安装的软件并把它安装在本地计算机的过程。所谓的软件源，就是我们获取软件的来源，它是定义在/etc/apt/sources.list文件里的。
默认的sources.list文件内容如下：
#
# deb cdrom:[Ubuntu-Server 16.04.2 LTS _Xenial Xerus_ - Release amd64 (20170215.8)]/ xenial main restricted
#deb cdrom:[Ubuntu-Server 16.04.2 LTS _Xenial Xerus_ - Release amd64 (20170215.8)]/ xenial main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://us.archive.ubuntu.com/ubuntu/ xenial main restricted
# deb-src http://us.archive.ubuntu.com/ubuntu/ xenial main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb http://us.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
# deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ xenial universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ xenial universe
deb http://us.archive.ubuntu.com/ubuntu/ xenial-updates universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-updates universe
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://us.archive.ubuntu.com/ubuntu/ xenial multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://us.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu xenial partner
# deb-src http://archive.canonical.com/ubuntu xenial partner
deb http://security.ubuntu.com/ubuntu xenial-security main restricted
# deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://security.ubuntu.com/ubuntu xenial-security universe
# deb-src http://security.ubuntu.com/ubuntu xenial-security universe
deb http://security.ubuntu.com/ubuntu xenial-security multiverse
# deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse
可以看到，官方的默认源是来自美国的us.archive.ubuntu.com和security.ubuntu.com。那么我们怎么样换成速度更快的国内源呢？很简单，把/etc/apt/sources.list文件复制备份一下，然后把原来的内容修改成国内源的网址即可。以下步骤说明以阿里云的源为例：
1、复制备份原来的配置文件
sudo cp /etc/apt/sources.list sources.list.bak
2、使用你喜欢的文本编辑器如vi/vim/nano，打开sources.list文件，把原来的内容替换成以下内容：
deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
##测试版源
deb http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse
# 源码
deb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
##测试版源
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse
# Canonical 合作伙伴和附加
deb http://archive.canonical.com/ubuntu/ xenial partner
deb http://extras.ubuntu.com/ubuntu/ xenial main
3、运行sudo apt-get update命令，更新软件列表，以后就可以使用阿里云提供的快速源了。同样的方法，也可以替换为网易源、搜狐源、中科大源、清华大学源等。