In Ubuntu, modifying the software source can speed up software updates and installations, especially for Chinese users, who can replace it with a mainland mirror source (such as Alibaba Cloud, Tsinghua, NetEase, etc.). The following is a detailed modification method:

　　1. Back up the original software source

　　Before modifying, it is recommended to back up the original sources.list file to prevent recovery after an error:

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

　　2. Edit the sources.list file

　　Use nano or vim to edit Ubuntu's software source list:

　　sudo nano /etc/apt/sources.list

　　Or:

　　sudo vim /etc/apt/sources.list

　　Clear the original content, and then select the appropriate software source according to your Ubuntu version.

　　3. Common software sources in mainland China

　　The following are common mirror sources in mainland China. Choose a suitable one to replace the content in sources.list:

　　(1) Alibaba Cloud Source

　　deb http://mirrors.aliyun.com/ubuntu/ jammy main restricted universe multiverse

　　deb http://mirrors.aliyun.com/ubuntu/ jammy-updates main restricted universe multiverse

　　deb http://mirrors.aliyun.com/ubuntu/ jammy-security main restricted universe multiverse

　　deb http://mirrors.aliyun.com/ubuntu/ jammy-backports main restricted universe multiverse

　　deb http://mirrors.aliyun.com/ubuntu/ jammy-proposed main restricted universe multiverse

　　(2) Tsinghua University Source

　　deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy main restricted universe multiverse

　　deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-updates main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-security main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-backports main restricted universe multiverse (3)NetEase source deb http://mirrors.163.com/ubuntu/ jammy main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ jammy-updates main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ jammy-security main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ jammy-backports main restricted universe multiverse

　　Description:

　　Ubuntu 22.04 corresponds to codename jammy

　　Ubuntu 20.04 corresponds to codename focal

　　Ubuntu 18.04 corresponds to codename bionic

　　Please replace jammy with the corresponding codename according to your system version.

　　4. Update software source

　　After the modification, press Ctrl + X to exit, press Y to save, and then execute:

　　sudo apt update && sudo apt upgrade -y

　　5. Restore the original software source (if an error occurs)

　　If the new source causes problems, you can restore the backup:

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

　　sudo apt update

　　Through the above method, your Ubuntu can be updated using the faster software source in the mainland!