In order to accomplish some upgrades, you need to boot to the “hard drive” instead of the network.  Some of the cases where booting to the hard drive are required:

• Uninstall PVS agent (to upgrade)
• Uninstall the Network Adapter (to replace or upgrade)
• Uninstall the Citrix Hypervisor tools (to upgrade)
• Upgrade the Operating System

If you do not have the original disk that was used to create the vDisk, you can create the hard disk from the PVS vDisk through ‘Reverse Image’.  

This article is specific to modern PVS deployments on Citrix Hypervisor and details one method only.  

Instructions

There are two choices for Step 1 - either boot the vDisk in Private mode, or boot to a maintenance version of the vDisk.  In this article we will keep it simple and boot to a maintenance version. 
Step 1 - Make a version of the disk that you need to reverse image, and choose a target device to boot into Maintenance Mode.  This is done in two steps. 

• In PVS console  Site >> vDisk Pool >> Right click the vDisk to reverse image (the image that needs the OS to be upgraded) >> Versions >> click the “New” button to make a maintenance version.  Click Done.
• Next, In PVS console >> Site >> Device Collection.  Choose a target device that will boot the maintenance version.  Right click the target device >> Properties.  Change ‘Type’ to Maintenance.

Step 2 - In the hypervisor, add a disk that is the same size or larger than the C: drive + the system reserved. 

Note: If the disk is low on space, you can add a bigger disk and then change the capacity when creating the reverse image in Step 7 below. 

Step 3 - If you chose to use a maintenance version, open the console of the target device in the Hypervisor console so that you can choose the maintenance vDisk for booting. 

Step 4 - Log into the target device.  Format the disk that was added above.  The type should be MBR for BIOS and GPT for UEFI.  Make sure there are no other disks attached and that there is no ISO mounted. 

Step 5 - Start P2PVS.  This is at C:\Program Files\Citrix\Provisioning Services.

Step 6 - Choose "Citrix Provisioning vDisk" to This Machine.

Step 7 - Inspect the Source and Destination.  The machine already knows how big the other drive is, and you can increase the capacity here. 

Step 8 - Click "Convert". 
Note:  You might see some things pop up about formatting drives.  Ignore these prompts and wait until the utility is finished. 

Step 9 - After you see this success message, shut down the target device. 

Step 10 - In the hypervisor console, change the boot options.  Deselect Network and Move Hard Disk up to the top of the list.

Step 11 - start the virtual machine.  You now have a virtual machine that is a duplicate of the PVS vDisk.  You can uninstall PVS, XenTools, Citrix Virtual Apps & Desktops and upgrade the operating system, the virtual hardware, the XenTools or whatever else is required. 

Tidy up:  Delete the maintenance version in PVS vDisk Versions.   

If you delete your target device that you used for the reverse image process, PVS will delete the account from Active Directory.