There is no shortage of articles online about building Windows images for use in various clouds. What there is a shortage of are working articles on building these images unattended. The Windows unattended install process has been basically solved, even if still a bit arcane. But finding more than a trivial example of doing it in a cloud is sparse. Cloudbase has shared the tooling they created for building their Windows images. That makes a good base for an automated build process that can be tailored to your particular needs. in addition to being the authors of cloudbase-init, their GitHub