How to change between a Full Installation (GUI) and Server Core in Windows Server 2012

Adding the GUI to a Server Core Installation
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Install-WindowsFeature Server-Gui-Shell, Server-Gui-Mgmt-Infra

Restart the server, once installed with the following command.

Restart-Computer
The installation will hang at 68% and after a while display an error message:
Install-WindowsFeature: The request to add or remove features on the specified server failed.

Follow these steps to solve this:

mkdir c:\mount

dism /get-wiminfo /wimfile:d:\sources\install.wim

Mount the WIM file

dism /mount-wim /wimfile: d:\sources\install.wim /index:4 /mountdir:c:\Mount\ /readonly

Install and specify the source:
Install-WindowsFeature Server-Gui-Shell, Server-Gui-Mgmt-Infra -Source C:\Mount\Windows\WinSXS

 

Restart the server, once installed.

 

Restart-Computer

 

 

 

Removing the GUI from a full installation, using Powershell:

Uninstall-WindowsFeature Server-Gui-Shell, Server-Gui-Mgmt-Infra

 

 

 

 

Ref:
http://www.danielclasson.com/how-to-change-between-a-full-installation-gui-and-server-core-in-windows-server-2012/
http://blog.coretech.dk/kaj/why-i-cant-convert-my-windows-server-2012-r2-core-to-gui/