Recently DigitalOcean introduced CoreOS support as long as it's metadata service. The service allows to set custom user data to provision new droplet.

Unfortunately, user data can't be edited after droplet is created. It reminded me the concept of immutable infrastructure when servers are considered as replaceable resources.

The article in the topic brings Ansible into toolbox for CoreOS cluster management. This approach looks promising.

How do you manage CoreOS machines? Do you use configuration management tools?