Sunday, 8 November 2020

Tip for capturing custom Windows 10 multi-session image for WVD

Azure gives us a nifty feature for capturing images from virtual machines. The high-level process is as follows:
  • Create the VM with Windows 10 multi-session
  • Install apps and customize
  • Snapshot the VM for future use
  • Sysprep and generalize the image
  • Capture the image
  • The image is then available in the gallery for creating WVD host pools

You'll find the capture feature in the Overview of the VM. Note that the capture renders the VM unusable and you can check a box to automatically delete the VM. If you want to revert you will have to create a new VM and apply the snapshot.

That all sounds great so what is the problem? The problem is actually a well known issue with capturing custom Windows 10 images. If you allow the reference computer (often a Hyper-V VM) to connect to the internet then the device can connect to the Windows 10 Store and update the built-in apps. This can cause Sysprep to fail. 


The easy way around that is to remove the NIC from the VM so that this cannot happen. 

However what can we do in Azure? You can't remove the NIC as you wouldn't be able to access the VM in that case. 


This is the Sysprep error I was seeing on my Azure reference computer. 

SYSPRP Failed to remove staged package Microsoft.PPIProjection_10.0.18362.449_neutral_neutral_cw5n1h2txyewy: 0x80070002.[gle=0x00000002]

I needed to prevent internet access but still maintain network access. DNS to the rescue. Normally a VM inherits DNS settings from the virtual network. However you can configure a custom DNS server for any VM. If you configure a DNS server that doesn't exist then the VM will not be able to access the internet but you still retain network access.

Click on the network interface for the VM.
 

You'll find that in the Networking blade.


Configure the dummy DNS server. Remember you have to be quick. Do this as soon as the VM is created. This worked for me and I was able to successfully syprep and capture the image. 

I hope this helps. Until next time........

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