This document discusses alternative approaches to contextualization for Windows virtual machines. It notes issues with the current approach using context.ps1, which requires reboots and has no mechanism for automatic Active Directory domain joining. The document proposes using Unattend.xml, which allows Windows to be configured during initial setup without reboots. It describes a method to dynamically generate Unattend.xml by calling a script via the OpenNebula FILES attribute, replacing VM parameters. Testing showed the Unattend.xml approach boosted a Windows VM from a 7 minute boot time to 3 minutes and 30 seconds without additional reboots.

1. © 2016 BlackBerry. All Rights Reserved. 1
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Alternative Contextualization for Windows
 Issues with current contextualization
 Current mechanism (context.ps1) requires a reboot to set the hostname
 Context.ps1 has no mechanism for joining AD domains automatically
 Alternative contextualization packages (e.g. cloud-init) have poor OpenNebula support
 Rebooting costs iops and time. Initializing the PowerShell environment takes time and iops
 Alternative contextualization
 Windows already has a native contextualization mechanism – Unattend.xml
 It is possible to have setup.exe search an external device for unattend.xml (e.g. context iso)
 Need to convert from context.sh to unattend.xml that setup.exe can understand.
 Currently, it is somewhat difficult to dynamically generate a file for a booting VM with a script.
 Can’t be done on the VM as the file is required for the VM to boot.
 Can’t be done ahead of time as we don’t know any of the parameters we need to set (e.g. IP address)
 Hooks don’t work as the script must block VM startup until it has completed.
 It would be really nice if OpenNebula supported a mechanism for calling a script to generate a file to go on the context iso as a VM is booting.

2. © 2016 BlackBerry. All Rights Reserved. 2
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Alternative Contextualization for Windows 2
 Context FILES attribute to the rescue…
 We can substitute VM parameters specific to the VM in this parameter (e.g. VM ID)
 The FILES attribute can reference an external source - e.g. webserver.
 FILES="http://context-helper/cgi-bin/makeunattend/$VMID/Unattend.xml",
 Webserver:
 Takes the VM ID, queries the frontend for the parameters assigned to this VM
 Takes a template Unattend.xml and populates it with the parameters retrieved earlier
 Unattend.xml is placed on the context iso, and is available to the booting VM.
 Result:
 Windows test VM with context.ps1, boots in 7m (including 2 reboots to rename and join AD)
 Windows test VM with unattend.xml boots in 3m 30s to a usable login prompt, with no further rebooting required.
 Source
 https://github.com/Batz-10K/FastContext