Ubuntu 20.04系统更改apt源为阿里源

以阿里源为例

1、备份源文件

sudo cp /etc/apt/sources.list /etc/apt/sources.list-bak

2、查看版本代号

lsb_release -c

每个版本的代号是不一样的，比如：

Ubuntu 18.04代号为：bionic

Ubuntu 19.04代号为：disco

Ubuntu 20.04代号为：focal

所以每个版本的修改方式稍微会有点区别

3、编辑sources.list文件

vim /etc/apt/sources.list

sources.list里的每个条目都是有格式的：

deb http://site.example.com/debian distribution component1 component2 component3 deb-src http://site.example.com/debian distribution component1 component2 component3

后面的几个参数是对软件包的分类（ubuntu下是main、restricted、universe、multiverse）。
格式如下：

deb 源URL 版本代号 main restricted universe multiverse
deb-sr 源URL 版本代号 main restricted universe multiverse

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

4、更新软件列表 和 软件包

# 更新软件列表
sudo apt-get update
# 更新软件包
sudo apt-get upgrade
echo $?
0