How to change from Evaluation to the real stuff in Windows Server 2012 R2

Step-by-Step

• Start an elevated command or powershell prompt.
• Execute “slmgr /dlv” to get information on the current status.

• Execute “dism /online /get-currentedition” to get the current edition, it should be an Evaledition

• Execute “dism /online /set-edition:ServerStandard /productkey:D2N9P-3P6X9-2R39C-7RTCD-MDVJX /accepteula”
• The key in this case is the KMS Client key for Windows Server 2012 R2 and you can get all those keys from
  http://technet.microsoft.com/en-us/library/jj612867.aspx

• Restart the server (it will reboot twice)
• Done

(https://deploymentbunny.com/2013/10/17/nice-to-know-how-to-change-from-evaluation-to-the-real-stuff-in-windows-server-2012-r2/)
(https://theitbros.com/activate-windows-with-kms-server/)