Windows Server 2012 Requirements and Installation : Switching Between Install Modes

6/14/2013 5:12:02 PM

No matter which installation option you chose, thanks to the flexibility of Server 2012, you can switch install modes after installation without losing existing configurations.

What are the benefits of switching from the full interface to a Server Core install or a Server Core install to the full interface? One reason could be the full install is consuming too many server resources. Maybe you want to reduce the threat attack surface that comes with a full installation. Or, perhaps you have become comfortable enough administering the server through PowerShell that you can afford to streamline the server and get rid of the full interface.

Whatever your reason, you have a couple of options to convert from the full install mode. You can convert through a simple PowerShell command, or you can remove the graphical shell of a full install to trim down to a core install.

Converting Server Core to Server with a GUI

To convert a Server Core install into a Server with a GUI install, you will need to create a folder to mount a Windows Imaging File (WIM). WIM files are images of the operating system and reside on the installation media, in the sources folder. The image file that gets mounted is the install.wim file, which is located inside the sources folder.

To get started, first run the command mkdir from the command prompt to create a directory named mountdir. The syntax is mkdir c:\mountdir. (See Figure 1.)

Figure 1. Creating a directory named mountdir for mounting the WIM file

After you run the mkdir command, the mountdir folder is listed under the root of the C:\ drive (see Figure 2).

Next, you need to find the index number associated with the Server with a GUI image you want to install. For example, I am converting from Server Core with the Datacenter edition of Windows Server 2012. I want to find the Server with a GUI image located on my installation media and the index number that references that image. To do so, use the Dism command at an elevated command prompt. The proper syntax is runas /user:administrator to elevate permissions within the command prompt. Click Enter, and you will be prompted to enter the administrator password.

Figure 2. Newly created mountdir directory

Then run the following to get the correct index number (also shown in Figure 3):

Dism /get-wiminfo  /wimfile:drive where installation media 
is located:\sources\install.wim

Figure 3. Command to locate the index number of the appropriate Server with a GUI image

Upon successfully running the command, you’ll see the Deployment Image Servicing and Management tool load. Find the index number of the Server with a GUI image you want to install (see Figure 4).

Figure 4. List of image files and associated index numbers

Mount the appropriate image file with the following command (also shown in Figure 5):

Dism /mount-wim /WimFile:drive where installation media is 
located:\sources\install.wim  /Index:#_from_step_2 /MountDir:c:\mountdir/readonly

This again launches the Deployment Image Servicing and Management tool. The Server with a GUI image is mounted.

After the message “The operation completed successfully” appears on screen, the image mount is complete. The final step requires installing the GUI from the mounted image with PowerShell. Launch PowerShell by simply typing powershell at the command line. Again, you must run PowerShell with the administrator account’s elevated permissions for the installation to work.

Run the cmdlet:

Install-WindowsFeature Server-Gui-Mgmt-Infra,Server-Gui-Shell –Restart –Source 
c:\mountdir\windows\winsxs

Figure 5. Mounting the image file

If the cmdlet is successfully executed, you will see the GUI installation start within PowerShell (see Figure 6).

Figure 6. The GUI installation process within PowerShell

After install, the server reboots. When the server comes back up, the Ctrl-Alt-Delete screen is displayed. Login and the Server Core interface are now replaced with the full Windows 2012 Server shell.

You can also use Windows Update as the source, instead of a WIM file, by using this Windows PowerShell cmdlet (make sure you have an Internet connection):

 Install-WindowsFeature Server-Gui-Mgmt-Infra,Server-Gui-Shell –Restart

Converting Server with a GUI to Server Core

To convert from Server with a GUI to a Server Core installation with Windows PowerShell, run the following cmdlet:

Uninstall-WindowsFeature Server-Gui-Mgmt-Infra -restart

Successful execution of the preceding cmdlet starts the removal process of the server shell (see Figure 7).

Figure 7. Converting Server with a GUI to a Server Core install

The server reboots once the graphical interface is removed. When the server comes back up, after login, the core interface is loaded.

If you initially install with the Server with a GUI option and then use the preceding command to convert to a Server Core installation, you can later revert to a Server with a GUI installation without specifying a source. This is because the necessary files remain stored on the disk, even though they are no longer installed.

If you convert to a Server Core installation, Windows features, server roles, and GUI management tools that require a Server with a GUI installation will be uninstalled automatically. You can specify the -WhatIf option in PowerShell to see exactly which features will be affected by the conversion.