Comment 5 for bug 1536981

It is debian-cd based, there is a bzr tree available. There are a few more ubuntu specific additions - livefs creation (which is requested and done in launchpad) and fetching the d-i images.

The ubuntu fork of debian-cd is available here: https://code.launchpad.net/~ubuntu-cdimage/debian-cd/ubuntu

The things specific to s390x on ubuntu are here:
http://bazaar.launchpad.net/~ubuntu-cdimage/debian-cd/ubuntu/view/head:/tools/boot/xenial/boot-s390x

and

http://bazaar.launchpad.net/~ubuntu-cdimage/debian-cd/ubuntu/files/head:/data/xenial/s390x/

It is still pending to add El Torito booting to above, which I have started last week, and will propose for merging & deployment shortly.