Proxmox VE on an Ankra Cloud Server

#!/bin/bash
# Turns a fresh Debian 13 cloud server (one NIC, cloud-init + netplan) into a Proxmox VE 9 host.
# Stage 1 installs the Proxmox kernel and moves networking to ifupdown2; reboot, then run stage 2.
set -euo pipefail
export DEBIAN_FRONTEND=noninteractive
stage="${1:?usage: $0 1|2}"

if [ "$stage" = 1 ]; then
  interface=$(ip -o -4 route show default | awk '{print $5}' | head -1)
  mac=$(cat "/sys/class/net/$interface/address")
  ipv4=$(ip -o -4 addr show dev "$interface" scope global | awk '{print $4}' | head -1)
  gateway4=$(ip -o -4 route show default | awk '{print $3}' | head -1)
  ipv6=$(ip -o -6 addr show dev "$interface" scope global | awk '{print $4}' | head -1)
  gateway6=$(ip -o -6 route show default | awk '{print $3}' | head -1)
  mtu=$(cat "/sys/class/net/$interface/mtu")
  host=$(hostname -s)
  # Keep the resolvers the server was given; public ones only as a fallback.
  nameservers=$(resolvectl dns "$interface" 2>/dev/null | cut -d: -f2- | tr ' ' '\n' | command grep -v '^$' || true)

  # Proxmox needs the hostname to resolve to the public address, and cloud-init must stop managing it.
  sed -i "/[[:space:]]${host}\$/d;/[[:space:]]${host}[[:space:]]/d" /etc/hosts
  echo "${ipv4%/*} $host.local $host" >> /etc/hosts
  cat > /etc/cloud/cloud.cfg.d/99-proxmox.cfg <<'EOF'
manage_etc_hosts: false
preserve_hostname: true
network: {config: disabled}
EOF

  curl -fsSL https://enterprise.proxmox.com/debian/proxmox-archive-keyring-trixie.gpg \
    -o /usr/share/keyrings/proxmox-archive-keyring.gpg
  cat > /etc/apt/sources.list.d/pve-install-repo.sources <<'EOF'
Types: deb
URIs: http://download.proxmox.com/debian/pve
Suites: trixie
Components: pve-no-subscription
Signed-By: /usr/share/keyrings/proxmox-archive-keyring.gpg
EOF
  root_source=$(findmnt -no SOURCE /)
  boot_disk=$(lsblk -no PKNAME "$root_source" | head -1)
  boot_disk=${boot_disk:+/dev/$boot_disk}
  echo "grub-pc grub-pc/install_devices multiselect ${boot_disk:-$root_source}" | debconf-set-selections
  apt-get update
  apt-get -y full-upgrade
  apt-get -y install proxmox-default-kernel ifupdown2

  cat > "/etc/systemd/network/10-$interface.link" <<EOF
[Match]
MACAddress=$mac

[Link]
Name=$interface
EOF
  {
    echo "auto lo"
    echo "iface lo inet loopback"
    echo
    echo "auto $interface"
    echo "iface $interface inet static"
    echo "	address $ipv4"
    echo "	gateway $gateway4"
    echo "	mtu $mtu"
    if [ -n "$ipv6" ]; then
      echo
      echo "iface $interface inet6 static"
      echo "	address $ipv6"
      if [ -n "$gateway6" ]; then
        echo "	gateway $gateway6"
      fi
    fi
    echo
    echo "source /etc/network/interfaces.d/*"
  } > /etc/network/interfaces
  mkdir -p /etc/network/interfaces.d
  mkdir -p /root/netplan-backup && mv /etc/netplan/*.yaml /root/netplan-backup/ 2>/dev/null || true
  systemctl disable systemd-networkd.socket systemd-networkd systemd-networkd-wait-online systemd-resolved 2>/dev/null || true
  systemctl enable networking
  rm -f /etc/resolv.conf
  {
    echo "search local"
    for nameserver in $nameservers 1.1.1.1 8.8.8.8; do
      echo "nameserver $nameserver"
    done
  } | awk '!seen[$0]++' | head -4 > /etc/resolv.conf
  update-initramfs -u -k all
  echo "stage 1 done: reboot, then run stage 2"
fi

if [ "$stage" = 2 ]; then
  echo "postfix postfix/main_mailer_type select Local only" | debconf-set-selections
  echo "postfix postfix/mailname string $(hostname -f)" | debconf-set-selections
  apt-get -y install proxmox-ve postfix open-iscsi chrony dnsmasq
  # Proxmox SDN runs its own dnsmasq per zone; the system-wide instance must stay off.
  systemctl disable --now dnsmasq
  apt-get -y remove os-prober || true
  apt-get -y remove 'linux-image-*-cloud-amd64' || true
  update-grub
  rm -f /etc/apt/sources.list.d/pve-enterprise.sources /etc/apt/sources.list.d/ceph.sources
  pveversion
fi