This article will provide you with the steps required to change the ELM disk from unmanaged to managed using Microsoft Azure and Citrix App Layering. 

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Instructions

Note: The below is a condensed description of the official Azure guidance found here . Scroll down to the section, “Migrate using the Azure portal”. Please refer to the Azure documentation should the process fail.
 

1. Login to the azure portal
2. Locate then select the ELM from either the list of recent resources or via a search
3. Shutdown and stop the virtual machine
4. Click on “Disks” from the left side menu.

5. On the top of the Disks page, click on “Migrate to managed disks".

6. Click on “Migrate”, at the bottom of the page
7. Test the access to the ELM appliance via the console and the GUI. Contact Citrix for any issues with access to the GUI. 
    

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https://learn.microsoft.com/en-us/azure/virtual-machines/windows/convert-unmanaged-to-managed-disks