Prepare a clean Debian system and upgrade to proxmoxve.

Debian11(bullseye) -> ProxmoxVE 7.x
  1. Configure hosts

Assuming your public network IP is and your host name is sycblog, the /etc/hosts file is configured as follows: localhost sycblog
# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters  


hostname --ip-address
# return:
  1. Install PrxomoxVE
    echo "deb [arch=amd64] bullseye pve-no-subscription" > /etc/apt/sources.list.d/pve-install-repo.list
    wget -O /etc/apt/trusted.gpg.d/proxmox-release-bullseye.gpg 
    apt update && apt full-upgrade
    apt install proxmox-ve postfix open-iscsi
    systemctl reboot
  1. Test and complete the upgrade
apt remove linux-image-amd64 'linux-image-5.10*'
apt remove os-prober