A cloud-init playground in Docker (ubuntu 16.04).
Run it one-time with docker-compose run dev.
Edit seed/user-data file.
Re-run.
Profit.
Or do docker-compose run dev bash, and rm -rf /var/lib/cloud/instance* && cloud-init init && cloud-init modules --mode=config && cloud-init -d modules --mode=final. Any changes to the seeds/user-data will be picked-up.