Debian11 更换软件源
准备工作，查看Debian版本：
cat /etc/os-release
1.切换用户
#切换root用户，普通用户也可以使用sudo命令
su
2.备份
#备份软件源列表
cp /etc/apt/sources.list /etc/apt/sources.list.bak
3.编辑sources.list
#也可以使用 vim编辑
gedit /etc/apt/sources.list
替换为下面的内容：
#http://mirrors.163.com/debian/为软件源也可以为其他的 bullseye为版本代号 main non-free
contrib区别如下
deb http://mirrors.163.com/debian/ bullseye main non-free contrib
deb http://mirrors.163.com/debian/ bullseye-updates main non-free contrib
deb http://mirrors.163.com/debian/ bullseye-backports main non-free contrib
deb-src http://mirrors.163.com/debian/ bullseye main non-free contrib
deb-src http://mirrors.163.com/debian/ bullseye-updates main non-free contrib
deb-src http://mirrors.163.com/debian/ bullseye-backports main non-free contrib
#deb http://mirrors.163.com/debian-security/ bullseye/updates main non-free contrib
#deb http://mirrors.ustc.edu.cn/debian-security/ bullseye/updates main non-free contrib
#deb-src http://mirrors.163.com/debian-security/ bullseye/updates main non-free contrib
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye main contrib non-free
deb https://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye-updates main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye-updates main contrib non-
free
deb https://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye-backports main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye-backports main contrib
non-free
deb https://security.debian.org/debian-security bullseye-security main contrib non-free
# deb-src https://security.debian.org/debian-security bullseye-security main contrib non-
free
区域 软件包数量 软件包组件标准
main 62089 遵从 Debian 自由软件指导方针（DFSG），并且不依赖于non-free
contrib 351 遵从 Debian 自由软件指导方针（DFSG），但依赖于non-free
non-free 770 不遵从 Debian 自由软件指导方针（DFSG）
更新软件源：
apt-get update