第一步：先把source.list文件备份

sudo mv /etc/apt/source.list /etc/apt/source.list.bak

第二步：修改source.list文件

sudo vi /etc/apt/source.list

第三步：把以下代码复制进去

deb https://mirrors.tuna.tsinghua.edu.cn/debian/ trixie main contrib non-free non-free-firmware
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ trixie main contrib non-free non-free-firmware

deb https://mirrors.tuna.tsinghua.edu.cn/debian/ trixie-updates main contrib non-free non-free-firmware
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ trixie-updates main contrib non-free non-free-firmware

deb https://mirrors.tuna.tsinghua.edu.cn/debian/ trixie-backports main contrib non-free non-free-firmware
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ trixie-backports main contrib non-free non-free-firmware

deb https://security.debian.org/debian-security trixie-security main contrib non-free non-free-firmware
# deb-src https://security.debian.org/debian-security trixie-security main contrib non-free non-free-firmware

• 以上为清华大学配置源