在购买服务器（VPS）后，一些商家的预装系统经常会出现各种软件和依赖包不能正常安装，这基本都是源引起的，进行更换源后即可正常。
为了减少不必要的麻烦，先执行以下命令将源文件进行备份
mv /etc/apt/sources.list /etc/apt/sources.list.bak
在下列的标签里选择一个你想换的源，复制命令在ssh执行即可
cat > /etc/apt/sources.list << EOF
deb http://deb.debian.org/debian/ bullseye main contrib non-free
deb-src http://deb.debian.org/debian/ bullseye main contrib non-free
deb http://deb.debian.org/debian/ bullseye-updates main contrib non-free
deb-src http://deb.debian.org/debian/ bullseye-updates main contrib non-free
deb http://deb.debian.org/debian/ bullseye-backports main contrib non-free
deb-src http://deb.debian.org/debian/ bullseye-backports main contrib non-free
deb http://deb.debian.org/debian-security/ bullseye-security main contrib non-free
deb-src http://deb.debian.org/debian-security/ bullseye-security main contrib non-free
EOF
cat > /etc/apt/sources.list << EOF
deb http://mirrors.tencentyun.com/debian/ bullseye main contrib non-free
deb-src http://mirrors.tencentyun.com/debian/ bullseye main contrib non-free
deb http://mirrors.tencentyun.com/debian/ bullseye-updates main contrib non-free
deb-src http://mirrors.tencentyun.com/debian/ bullseye-updates main contrib non-free
deb http://mirrors.tencentyun.com/debian/ bullseye-backports main contrib non-free
deb-src http://mirrors.tencentyun.com/debian/ bullseye-backports main contrib non-free
deb http://mirrors.tencentyun.com/debian-security/ bullseye-security main contrib non-free
deb-src http://mirrors.tencentyun.com/debian-security/ bullseye-security main contrib non-free
EOF
cat > /etc/apt/sources.list << EOF
deb http://mirrors.cloud.aliyuncs.com/debian/ bullseye main contrib non-free
deb-src http://mirrors.cloud.aliyuncs.com/debian/ bullseye main contrib non-free
deb http://mirrors.cloud.aliyuncs.com/debian/ bullseye-updates main contrib non-free
deb-src http://mirrors.cloud.aliyuncs.com/debian/ bullseye-updates main contrib non-free
deb http://mirrors.cloud.aliyuncs.com/debian/ bullseye-backports main contrib non-free
deb-src http://mirrors.cloud.aliyuncs.com/debian/ bullseye-backports main contrib non-free
deb http://mirrors.cloud.aliyuncs.com/debian-security/ bullseye-security main contrib non-free
deb-src http://mirrors.cloud.aliyuncs.com/debian-security/ bullseye-security main contrib non-free
EOF
cat > /etc/apt/sources.list << EOF
deb http://mirrors.linode.com/debian/ bullseye main contrib non-free
deb-src http://mirrors.linode.com/debian/ bullseye main contrib non-free
deb http://mirrors.linode.com/debian/ bullseye-updates main contrib non-free
deb-src http://mirrors.linode.com/debian/ bullseye-updates main contrib non-free
deb http://mirrors.linode.com/debian/ bullseye-backports main contrib non-free
deb-src http://mirrors.linode.com/debian/ bullseye-backports main contrib non-free
deb http://mirrors.linode.com/debian-security/ bullseye-security main contrib non-free
deb-src http://mirrors.linode.com/debian-security/ bullseye-security main contrib non-free
EOF
在换源后还需要执行以下命令代码，更新系统索引，让新源生效。
apt update