要更换Debian的软件源，可以按照以下步骤进行：
打开终端。
编辑 /etc/apt/sources.list 文件，可以使用任何文本编辑器进行编辑，比如 nano：
sudo nano /etc/apt/sources.list
deb http://deb.debian.org/debian/ buster main
deb-src http://deb.debian.org/debian/ buster main
deb http://security.debian.org/debian-security buster/updates main
deb-src http://security.debian.org/debian-security buster/updates main
# buster-updates, previously known as 'volatile'
deb http://deb.debian.org/debian/ buster-updates main
deb-src http://deb.debian.org/debian/ buster-updates main
deb https://mirrors.tuna.tsinghua.edu.cn/debian/ buster main contrib non-free
deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ buster main contrib non-free
sudo apt update
这样就成功更换了Debian的软件源。
