对于Ubuntu系统， 不同的版本的源都不一样，每一个版本都有自己专属的源。 而对于 Ubuntu 的同一个发行版本，它的源又分布在全球范围内的服务器上。Ubuntu 默认使用的官方源的服务器在欧洲，从国内访问速度很慢。国内的阿里、网易以及一些重点高校也都有 Ubuntu 的源，所以在装完 Ubuntu 系统后最好把官方源更换为国内的源。
1.获取Ubuntu代号
Ubuntu 每个发行版本都有自己的代号，我们要通过我们电脑上 Ubuntu 的代号去找对应的源，Ctrl+Alt+T 打开终端，执行以下命令：
lsb_release -a
然后会得到我们自己的 Ubuntu 的版本信息 ，最后一栏 codename 后面的就是我们自己的 Ubuntu 的代号。比如我安装的是 Ubuntu 18.04.1，查出来的代号就是 bionic.
2.查找可用的源
https://wiki.ubuntu.org.cn/源列表
3.编辑源
打开链接：https://wiki.ubuntu.org.cn/模板:18.04source
复制以下内容到编辑器：
将上图ubuntu18.4源模板里红框内的ubuntu默认官方源地址改为step2里面任意一个服务器地址，一般用阿里云和清华大学的源；然后将蓝色框中的内容改为你自己Ubuntu的代号。
例如：
# 1.阿里云源 deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse ##測試版源 deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse # 源碼 deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse ##測試版源 deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse # 2.清华大学源 deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse ##測試版源 deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse # 源碼 deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse ##測試版源 deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
4.修改源文件source.list
Ubuntu 的源存放在在 /etc/apt/ 目录下的 sources.list 文件中，修改前我们先做个备份，在终端中执行以下命令：
sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup
然后执行下面的命令打开 sources.list 文件，清空里面的内容，把上面我们编辑好的国内的源复制进去，保存后退出。
sudo gedit /etc/apt/sources.list
5.更新软件包列表
sudo apt-get update
6.更新软件
sudo apt-get upgrade
或者
sudo apt-get dist-upgrade
这里提一下apt-get upgrade 与apt-get dist-upgrade的关系：
upgrade:系统将现有的Package升级,如果有相依性的问题,而此相依性需要安装其它新的Package或影响到其它Package的相依性时,此Package就不会被升级,会保留下来.
dist-upgrade:可以聪明的解决相依性的问题,如果有相依性问题,需要安装/移除新的Package,就会试着去安装/移除它. (所以通常这个会被认为是有点风险的升级)
ubuntu 16.04 source
# 东北大学 deb-src http://mirror.neu.edu.cn/ubuntu/ xenial main restricted #Added by software-properties deb http://mirror.neu.edu.cn/ubuntu/ xenial main restricted deb-src http://mirror.neu.edu.cn/ubuntu/ xenial restricted multiverse universe #Added by software-properties deb http://mirror.neu.edu.cn/ubuntu/ xenial-updates main restricted deb-src http://mirror.neu.edu.cn/ubuntu/ xenial-updates main restricted multiverse universe #Added by software-properties deb http://mirror.neu.edu.cn/ubuntu/ xenial universe deb http://mirror.neu.edu.cn/ubuntu/ xenial-updates universe deb http://mirror.neu.edu.cn/ubuntu/ xenial multiverse deb http://mirror.neu.edu.cn/ubuntu/ xenial-updates multiverse deb http://mirror.neu.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse deb-src http://mirror.neu.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse #Added by software-properties deb http://archive.canonical.com/ubuntu xenial partner deb-src http://archive.canonical.com/ubuntu xenial partner deb http://mirror.neu.edu.cn/ubuntu/ xenial-security main restricted deb-src http://mirror.neu.edu.cn/ubuntu/ xenial-security main restricted multiverse universe #Added by software-properties deb http://mirror.neu.edu.cn/ubuntu/ xenial-security universe deb http://mirror.neu.edu.cn/ubuntu/ xenial-security multiverse
# 清华大学 # deb cdrom:[Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)]/ xenial main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security multiverse
# 阿里云 # deb cdrom:[Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)]/ xenial main restricted deb-src http://archive.ubuntu.com/ubuntu xenial main restricted #Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted deb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted multiverse universe #Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted multiverse universe #Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial universe deb http://mirrors.aliyun.com/ubuntu/ xenial-updates universe deb http://mirrors.aliyun.com/ubuntu/ xenial multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-updates multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse #Added by software-properties deb http://archive.canonical.com/ubuntu xenial partner deb-src http://archive.canonical.com/ubuntu xenial partner deb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted multiverse universe #Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial-security universe deb http://mirrors.aliyun.com/ubuntu/ xenial-security multiverse
Ubuntu 16.04的ARM源
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-updates main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-security main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-backports main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-proposed main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial main restricted universe multiverse
Ubuntu 18.04的ARM源
# 2.清华大学源 deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse ##測試版源 deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-proposed main restricted universe multiverse