gist-fix-vm-boot.sh

#!/bin/bash
# Fix Proxmox VM Initramfs/GRUB Issues After Cloning
# Run from Ubuntu Live ISO - Select "Try Ubuntu"
# wget https://gist.githubusercontent.com/YOUR_USERNAME/GIST_ID/raw/fix-vm-boot.sh
# sudo bash fix-vm-boot.sh

set -e

# Check root
[ "$EUID" -ne 0 ] && { echo "Run with sudo: sudo bash $0"; exit 1; }

# Detect disk
if [ -b /dev/sda ]; then DISK="/dev/sda"; else DISK="/dev/vda"; fi
echo "Using disk: $DISK"

# Mount filesystems
mkdir -p /mnt/root
mount ${DISK}2 /mnt/root
mount ${DISK}1 /mnt/root/boot/efi
mount --bind /dev /mnt/root/dev
mount --bind /proc /mnt/root/proc  
mount --bind /sys /mnt/root/sys

# Fix boot in chroot
chroot /mnt/root /bin/bash -c '
  # Install GRUB
  grub-install /dev/sda 2>/dev/null || grub-install /dev/vda
  update-grub
  
  # Add virtio modules
  echo -e "virtio_scsi\nvirtio_blk\nvirtio_pci\nvirtio_net" >> /etc/initramfs-tools/modules
  sort -u /etc/initramfs-tools/modules > /tmp/m && mv /tmp/m /etc/initramfs-tools/modules
  
  # Rebuild initramfs
  update-initramfs -u -k all
'

# Cleanup
umount -R /mnt/root

echo "Fixed! Reboot with: sudo reboot"
echo "After boot: qm set VMID --boot 'order=scsi0;ide2;net0'"