Omnissa Horizon on Nutanix AHV with Golden Image creation

In this blogpost I will describe how to connect Omnissa Horizon against a Nutanix AHV cluster and how to setup the golden image. We are going for an RDS setup because we can 😉

The steps involved are:

1. Connect Omnissa Horizonagainst the Nutanix cluster (capacity provider);
2. Create a Compute Profile;
3. Create the Windows Server 2025 Golden Image;
4. Create the “farm”;
5. Happy working 😉

Before we continue make sure Omnissa Horizon is running version 2512 and your Nutanix environment is running minimum:

• Prism Central (PC): Version 2024.3 or newer;
• Nutanix AOS: Version 7.0 or newer;
• Nutanix AHV: Version 10.0 or newer.

If all minimum versions are in place we can continue. First we start with connecting the Omnissa Environment against Prism Central (Yes Prism Central). Open the Omnissa webconsole and navigate to: Settings –> Servers –> Capacity Providers –> ADD.

Fill in all information, (Yes I created a service account for Omnissa local on Prism Central. I don’t want to be dependent of active directory for this) and click OK.

When the connection is successful we need to create a Compute Profile. This is the profile used for the created virtual machines. In my case my RDS Terminal Servers must have a profile of 6 vCPU, 16GB memory and a vTPM. Click on: Settings –> Capacity Provider Settings –> Computer Profiles –> ADD.

Add your required profile. For the 6vCPU requirements Omnissa will create 6 CPU’s with each 1 core. I dont like this and I normally do this the other way arround (1 CPU with 6 cores). But for Nutanix performance wise it doesn’t matter 😉 It is only my OCD 😉 Click OK.

Now we are done with the basic configuration. Lets create a Windows Server 2025 Terminal Server Golden Image (that is a mouth full). The easiest method is using my VirtIO Slipstream script to create a Windows installation ISO with the VirtIO drivers already present. This will help you with fast setup times. You can find the script here.

Create a virtual machine with the following specs:

• Name: Windows Server 2025 Terminal Server Golden Image (Choose your own name ;))
• CPUs: 6
• Cores per CPU: 1
• Memory: 16GB
• Attach a SCSI Disk: 100GB (Or the size needed for you deployment). Make sure you place the disk in the correct storage container with the correct features enabled.
• Attach a SATA CD-ROM: And mount the Windows installer which is prepared with the VirtIO drivers
• Network: Your VLAN/Subnet where the Terminal Servers should reside. This can be a managed subnet or even an advanced (Flow microsegmentation) subnet.
• Boot Configuration: UEFI
• VM Security Settings: Enable vTPM

When Windows is installed, eject the cd-rom and make it domain member. We don’t need the Nutanix Guest Tools so don’t install them. If not using the latest NGT 4.5 then it doesn’t work either. In a Terminal Server (or even VDI) we are not using functionality which the NGT provide. So don’t install it. Next install the Omnissa agent.

I want this deployment to use the terminal server as a multi user server so I need to select RDS mode. This will automatically install the RDS session Host role and reboots te server. Restart the Horizon agent setup again to continue. Select that this machine will be used as a Golden Image and click Next.

Deselect the Instant Clone Agent as that is not how Nutanix works 😉 Nutanix has shadow clones built in for years now. Scroll down and enable Horizon Performance Tracker. Click Next.

On the next screen enter the connection server FQDN or IP address. There is a typo in the installer as is says: “hostname or IP address” but hostname is working but should not be used ; . I hope Omnissa will change this to “FQDN or IP address”. Enter the administrator credentials (Omnissa admin) and click: Next.

Run Windows Update and install all your applications. For most default applications I always use Manuel Winkel his NeverRed script: https://www.deyda.net/index.php/en/neverred/ (Pretty easy). When all applications are installed and Windows update is done we are going to start the Omnissa Horizon Optimization Tool.

!!! WARNING !!! OSOT does not supported (yet) Windows Server 2025. Don’t run it on Windows Server 2025 as this will break your Golden Image.
Use the Citrix optimization tool (for example) for now.

The steps below are just for references. 😉 For when it will be supported.

Important: Run this when logged in with a local admin account. Don’t run this when logged in with a domain user/admin account or else you end up with cached credentials (and profile) from that user in the golden image. (Deleted all cached credentials/profiles from the domain accounts)

We are not using the Windows Audit mode to seal the Golden Image. This makes creating the updates way more difficult including automating this process. So we stick to the good old method 😉 This means we are skipping generalize in the Optimization Tool.

I’m not covering all the Optimization steps in this blogpost. As that is very well documented on other blogs already. We don’t have to use the “sdelete” as Nutanix works with extends and all disks always thin provisioned. 😉 But the method is:

1. Analyze;
2. Change settings in Common Options;
3. Export the settings (to use when running optimization again)
4. Optimize
5. Change settings in Finalize;
6. Finalize.

There are more steps to do before a golden image is sealed correctly. For example always run a full virusscan before shutting down, etc

When done, shutdown the virtual machine. In Prism Central select the Golden Image virtual machine and remove the CD-Rom drive. Select the Golden Image Virtual Machine again and select Create VM Template from the action/context menu:

The next steps are next next finish. And the template is created. For more deep dive into the templates functionality of Prism Central read the following two blogposts:

• https://www.jeroentielen.nl/creating-and-maintaining-a-template-virtual-machine-in-nutanix/
• https://www.jeroentielen.nl/nutanix-guest-customization-profiles/

Now we need to create the “farm” in Omnissa. Click Inventory –> Farms –> ADD

Select: Automated Farm (as we are using virtual machines) I’m skipping steps which are self explaining 😉

Select you Nutanix Prism Central provider.

Select the template and make sure you also select the correct version inside the template.

Now select the profile we created for the Terminal Servers. Scroll down and also select in which network the virtual machines must be placed.

Select the correct OU to place the virtual machines in. For the customization we select ClonePrep.

When done you will end up with the following machines (depending how much RDS servers are requested to be generated).

The it-termblablabla is the internal vm used for creating the actual machines. RDS-1 is my new terminal server. And, of course, the Golden Image is still there. (can be removed if needed).

The machines are part of a category as well:

And that’s is. You can now publish desktops and applications as always within Omnissa Horizon.

When you need to do your (monthly) updates in the Golden Image. Follow my guide I created about creating and maintaining a template: https://www.jeroentielen.nl/creating-and-maintaining-a-template-virtual-machine-in-nutanix/ (Dont forget to run the optimization tool before shutting the machine down).