Currently we have 2008 R2 Standard as our KMS server in our environment. We need to upgrade the Server OS to Windows Server 2012 R2 to support Windows 10 activations. My question is, if we upgrade the server OS on the KMS server, do we need to start from scratch in setting up the KMS server or do we add only the Windows 10 KMS client key? This is going to be an in-place upgrade. Please advice...

Hi gvtri,

With Windows 10 activation, you KMS host must install the following hofix.

Update that enables Windows 8.1 and Windows 8 KMS hosts to activate Windows 10

https://support.microsoft.com/en-us/kb/3058168

Im glad to be of help to you!

Thank you! After we performed an in place upgrade, I had to run Windows Update to install a bunch of pre-requisite updates before installing this this update. Everything else went smooth after that... Thanks again for your help!