鏡像源是跟linux版本一一對應的,查詢自己系統的版本號：
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:~$ 

說明系統版本是 Ubuntu 20.04.6 LTS， 不是請跳過本文章。

1.備份sources.list文件

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

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

打開vim編輯器，把sources.list文件中所有的deb文件中未被注釋的，全部用#注釋掉然后把上面給的國內鏡像復制去就可以，并：wq！保存

3.更新

sudo apt update
sudo apt upgrade