更换Ubuntu源为国内源的操作记录

首先了解下/etc/apt/sources.list.d文件
文件/etc/apt/sources.list是一个普通可编辑的文本文件，保存了ubuntu软件更新的源服务器的地址。
和sources.list功能一样的是/etc/apt/sources.list.d/*.list(*代表一个文件名，只能由字母、数字、下划线、英文句号组成)，
该文件夹下的文件是第三方软件的源，可以分别存放不同的第三源地址，只需“扩展名”为list即可。
sources.list.d目录下的*.list文件为在单独文件中写入源的地址提供了一种方式，通常用来安装第三方的软件。

如下是ubuntu官方sources.list文件内容：
deb http://archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse

以上内容的具体含义如下：
1）每一行的开头是deb或者deb-src，分别表示直接通过.deb文件进行安装和通过源文件的方式进行安装。
2）deb或者deb-src字段之后，是一段URL，之后是五个用空格隔开的字符串，分别对应相应的目录结构。
在浏览器中输入http://archive.ubuntu.com/ubuntu/，并进入dists目录，可以发现有5个目录和前述sources.list文件中的第三列字段相对应。
任选其中一个目录进入，可以看到和sources.list后四列相对应的目录结构


以上官方的ubuntu源在国内使用，通常都会很慢，以至于在使用过程中报错。
----------------下面是我在线上使用过的一个ubuntu的源---------------------
root@ubuntutest03-KVM:~# cat /etc/apt/sources.list|grep -v "^#"|grep -v "^$"
deb http://cn.archive.ubuntu.com/ubuntu/ xenial main restricted
deb http://cn.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
deb http://cn.archive.ubuntu.com/ubuntu/ xenial universe
deb http://cn.archive.ubuntu.com/ubuntu/ xenial-updates universe
deb http://cn.archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://security.ubuntu.com/ubuntu xenial-security universe
deb http://security.ubuntu.com/ubuntu xenial-security multiverse

--------------下面是替换成阿里源的内容-------------
root@ubuntutest03-KVM:~# cat /etc/apt/sources.list
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

root@ubuntutest03-KVM:~# apt-get update 更新源  
root@ubuntutest03-KVM:~# apt-get upgrade 更新软件 


-------------更换成其他开放的ubuntu源，做法和上面同理----------------
再比如下面更换成网易源（打开文件中的url。进入dists目录下就能看到xenial等对应的目录结构了）
root@ubuntutest03-KVM:~# cat /etc/apt/sources.list
deb http://mirrors.163.com/ubuntu/ xenial main restricted
deb http://mirrors.163.com/ubuntu/ xenial-updates main restricted
deb http://mirrors.163.com/ubuntu/ xenial universe
deb http://mirrors.163.com/ubuntu/ xenial-updates universe
deb http://mirrors.163.com/ubuntu/ xenial multiverse
deb http://mirrors.163.com/ubuntu/ xenial-updates multiverse
deb http://mirrors.163.com/ubuntu/ xenial-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://security.ubuntu.com/ubuntu xenial-security universe
deb http://security.ubuntu.com/ubuntu xenial-security multiverse

root@ubuntutest03-KVM:~# apt-get update 更新源  
root@ubuntutest03-KVM:~# apt-get upgrade 更新软件