#  edit /etc/initramfs-tools/modules and add virtio, virtio_pci, virtio_ring, virtio_net, virtio_blk

echo "virtio" >>  /etc/initramfs-tools/modules
echo "virtio_pci" >>  /etc/initramfs-tools/modules
echo "virtio_ring" >>  /etc/initramfs-tools/modules
echo "virtio_net" >>  /etc/initramfs-tools/modules
echo "virtio_blk" >>  /etc/initramfs-tools/modules

# update the initramfs using update-initramfs -u 
update-initramfs -u