ubuntu 20.04 更改国内镜像源-阿里源 确保可用

镜像源是跟linux版本一一对应的,查询自己系统的版本号：
命令：lsb_release -a

ma@cw:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.6 LTS
Release:        20.04
Codename:       focal
ma@cw:~$ 

说明系统版本是 Ubuntu 20.04.6 LTS， 不是请跳过本文章。

1.备份sources.list文件

sudo cp /etc/apt/sources.list /etc/apt/sources.list.back

2.编辑sources.list文件

sudo vim /etc/apt/sources.list

deb https://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse

deb https://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse

deb https://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse

# deb https://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse

deb https://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse

打开vim编辑器，把sources.list文件中所有的deb文件中未被注释的，全部用#注释掉然后把上面给的国内镜像复制去就可以，并：wq！保存

3.更新

sudo apt update
sudo apt upgrade