Ubuntu 的軟件源配置文件是 /etc/apt/sources.list。將系統自帶的該文件做個備份，將該文件替換為下面內容，即可使用 TUNA 的軟件源鏡像。
備份Debian默認的源地址
sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup 執行vim /etc/apt/sources.list將下方代碼替換原來的代碼：
vim /etc/apt/sources.list
gedit /etc/apt/sources.list
# 默認注釋了源碼鏡像以提高 apt update 速度，如有需要可自行取消注釋 deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse # 預發布軟件源，不建議啟用 # deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
修改好后執行sudo apt-get update更新源
sudo apt-get update