1 Backup the original source files
Execute the following command to backup and save the original source file.
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
2 Modify the source file sources.list
Open the source file, comment (or directly delete) the original source, copy and paste Ali source or other sources to save
sudo gedit /etc/apt/sources.list
or sudo vi /etc/apt/souces.list
deb [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal main restricted universe multiverse
deb-src [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal main restricted universe multiverse
deb [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal-security main restricted universe multiverse
deb-src [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal-security main restricted universe multiverse
deb [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal-updates main restricted universe multiverse
deb-src [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal-updates main restricted universe multiverse
deb [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal-proposed main restricted universe multiverse
deb-src [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal-proposed main restricted universe multiverse
deb [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal-backports main restricted universe multiverse
deb-src [http://mirrors.aliyun.com/ubuntu/](http://mirrors.aliyun.com/ubuntu/) focal-backports main restricted universe multiverse
3 update source
Execute command in terminal
sudo apt update
sudo apt upgrade
