### 查看系统版本
cat /etc/debian_version
备份source-list文件：
cp /etc/apt/sources.list /etc/apt/sources.list.old
1.编辑source-list文件：
nano /etc/apt/sources.list
把下面这一行内容添加到第一行
deb http://deb.debian.org/debian bullseye main contrib
2.apt update
3.apt full-upgrade
