I have been running an Active Directory server for a very long time without any updates. It is time to upgrade it, or more accurately, to abandon it. By that I mean to install a new AD, hopefully synchronize to the old one, and then retire the old one. This is one area I've never had to become particularly competent in and that has come home to roost.
I'm looking for advice on how to do this gracefully so stuff doesn't break all over the place. While I have very few users, I do have lots of servers and services that depend on that to work.
I have access to Windows servers vintage 2008 R2, 2012 and 2016.