Last week, Microsoft introduced Windows Server Insider Preview version 17623, providing admins a preview on its upcoming Windows Server 2019 Long-term Servicing Channel (LTSC) release, scheduled for the second half of calendar year 2018.
While Microsoft strongly urges to validate the in-place upgrade functionality of Windows Server 2019 from Windows Server 2012 R2 and Windows Server 2016, one issue has already arisen in this area.
To paraphrase the Windows Server Insider Preview version 17623 release notes:
In‑place OS upgrade: Domain Controllers. During an in-place OS upgrade, Active Directory (AD) Domain Controllers (DC) might not be upgraded correctly. So, back up any AD DCs before performing an in-place OS upgrade.
I feel running a Windows Server Insider Preview build in a production environment to power your Active Directory Domain Controllers is only for a select few admins with a strong desire to feel alive again…. and have left Microsoft support far behind them.
However, in test and acceptance environments, this issue is something that might prove a challenge. It’s nothing new, however, since In-place upgrading an Active Directory Domain Controller to Windows Server build 17093 might also fail.