I'm trying to find the best-practice, modern way of doing what I used to do with python-vm-builder (aka ubuntu-vm-builder).

I want a scripted, repeatable way to start from something like ubuntu-core (aka the artist formerly known as JeOS), add some packages, define first-run scripts, etc.

What I'm after is something akin to spinning a custom ISO (although it wont be an ISO, it will be an "installed" system). The result needs to be a kernel, initrd image, and rootfs that is suitable for a diskless PXE boot with NFS.

What tools are used to create say the Ubuntu netboot image (or any Ubuntu images for that matter)? Are they flexible enough for my needs?

How about the tools used to create the fresh-install environments used for the Ubuntu integration testing? Would they be appropriate?

Note that at run time the rootfs will be mounted read-only, so I'm not looking to manage an instance over time. I'm looking to re-spin an automated install at each new Ubuntu release, and periodically in the 6 months between.