Creating a Windows image and making it ready for OpenShift Virtualization requires  installing and configuring several services and drivers.. This should be repeated each time you have  a new update from Microsoft or Red Hat, which may become error-prone and time consuming.

Lucky, there is a better way. Windows has a feature called unattended installation - similar to a kickstart file for RHEL - that is used as an answer file to the entire installation wizard. You could also add drivers and post scripts to complete the installation.

Windows Unattended XML

There is a windows tool called “Windows System Image Manager” (WSIM) that helps build the Unattended installation. You can find more information on how to use it in Microsoft’s documentation: (https://docs.microsoft.com/en-us/windows-hardware/customize/desktop/wsim/windows-system-image-manager-overview-topics )

Note: Windows Unattended installation may vary between different versions of Windows such as Windows Server 2019 , Windows Server Core 2019 etc. If you are supporting multiple Windows versions, we recommend creating a version of the Unattended XML for each version.

Post Installation Script

After installing the operating system, we need to add a few more services to support the Openshift Virtualization platform. During the Unattended installation we will add auto-login for the Administrator and a Powershell script for the first time logon.

In the post installation script, we will install  the Qemu Guest Agent and some additional Drivers, you can also add your own Service / application if needed.

At the end of the script we are disabling the Auto-Login feature and running sysprep with the shutdown option to complete the installation.

Running the Installation

Prerequisites

• Red Hat Enterprise Linux

Download the Windows image

In this guide we are using Microsoft Windows 2019 evaluation Server image which can be downloaded from the Microsoft website

https://www.microsoft.com/en-US/evalcenter/evaluate-windows-server-2019?filetype=ISO

1. Get an answer file and a post-installation script

Using the unattended installation XML and post script to complete the installation, drivers and Services.

Autounattended.xml

post-install.ps1

Install required packages

In some cases you would like to see the installation running, for that you will need to install the ”virt-viewer” package.

For a CI pipeline the UI is not needed.

Prepare Windows Image

In order to run the installation we need to add the unattended file and the postscript to the windows image.

Mount windows ISO

Copy ISO and files to a temp directory

Create a new bootable ISO from the temp directory

Run the Installation process

First, we need to create a disk image file

Don't forget to add the “qemu” user permission to the working directory

Next, we will run the installation script

If you’re running as a non-root user you should add the user to the libvirt group

Depending on the host, the installation will take about 5 - 20 minutes and the command will exit.

If you are running in a CI pipeline / remote server you can remove the “--connect qemu:///system” option from the command line

Finally we have a disk Image ready to be uploaded to the OpenShift Virtualization. First we will switch to the “openshift-virtualization-os-images” project and then push the image with the “virtctl” command.

In this command, we are using the “win2k19” as the image name. This name is taken from the image templates mentioned in https://github.com/kubevirt/common-templates.

If you’re running the cluster with self-sign certificate / untrusted certificate you should add the “--insecure” option to ignore the certificate verification.

To use the newly added image just create a new VM from wizard and select the windows2019 image. This will correlate to the image name with used “win2k19”

That’s it! We have a Windows Server 2019 image ready to be used. You can also add your own custom script and installation to the “post-install.ps1” if you want to install Anti-virus or some other application.