#cloud-config
## this can be utilized by booting an image that has a kernel
## command line like
##    ro root=/dev/vda url=https://smoser.brickies.net/ubuntu/nocloud
## Then, cloud-init will read:
##   https://smoser.brickies.net/ubuntu/nocloud/user-data
##     and
##   https://smoser.brickies.net/ubuntu/nocloud/meta-data
##   
## Take a stock precise .tar.gz file, get the kernel, the initramfs
## and then boot like:
##   qemu-img create -f qcow2 -b disk.img.dist disk.img;
##   kvm -drive file=disk.img,if=virtio -kernel kernel -initrd initrd -curses \
##     -append "ro root=/dev/vda url=https://smoser.brickies.net/ubuntu/nocloud"
##
datasource:
  NoCloudNet:
    seedfrom: http://smoser.brickies.net/ubuntu/nocloud/


This can be done with an official Ubuntu 18.04 image like:

qemu-system-x86_64 -enable-kvm -m 768 \
   -net nic -net user \
   -drive file=bionic-server-cloudimg-amd64.img,if=virtio \
   -smbios "type=1,serial=ds=nocloud-net;s=https://smoser.brickies.net/ubuntu/nocloud/"