原文出自：https://blog.csdn.net/csgd2000/article/details/81059461
vim /etc/apt/sources.list.d/pve-enterprise.list
注释掉
#deb https://enterprise.proxmox.com/debian/pve stretch pve-enterprise
也可以直接删除掉
rm -f /etc/apt/sources.list.d/pve-enterprise.list
为了更新proxmox 还需要
nano /etc/apt/sources.list
添加内容：
deb http://download.proxmox.com/debian stretch pve-no-subscription
echo "deb http://download.proxmox.com/debian/pve stretch pve-no-subscription" > /etc/apt/sources.list.d/pve-install-repo.list
wget http://download.proxmox.com/debian/proxmox-ve-release-5.x.gpg -O /etc/apt/trusted.gpg.d/proxmox-ve-release-5.x.gpg
apt update && apt dist-upgrade
官方文档：
https://pve.proxmox.com/wiki/Install_Proxmox_VE_on_Debian_Stretch
之后就可以正常使用
apt update && apt dist-upgrade
升级完成后，可以执行pveversion -v查看下最新的软件版本。然后执行reboot重启物理服务器