Native boot VHDs and MDT [3]

At the moment I am trying out the walkthrough applying a sysprepped image directly to a VHD file that I created with Diskpart. This tool can be used with VHD files as well as ordinary hard disks and then it can mount the VHD to a drive letter.

As noted in previous discussion while this gives me an image that has been sysprepped, what it doesn’t have is the injection of drivers for a target platform so I don’t know what will happen when it is booted up to a specific platform. The previous debate so far has been over ways to inject those drivers. If my walkthrough works I will have to move on to trying out the different forms of driver injection.

First problem on the walkthrough was that the PC is too old to run x64. OK so then I set up a VHD for x86, because I didn’t have a captured image for Ent x86 I used ImageX to apply install.wim directly from x86 Ent ISO. The rest went smoothly enough until reboot. Note that you need to use the Windows 7 version of ImageX, the version from WinPE 2.0 (Vista) does not support vdisk (VHD). In order to run this I used a MDT LiteTouch boot CD in command prompt mode. When I rebooted I got “Bootmgr is missing”. The problem seems to be that the instructions in the walkthrough are wrong in some way. The VHD was assigned drive letter C, but on reboot, the drive letter C has been reassigned to the computer’s physical disk, and there seems to be no way to make the letter C stay assigned to the VHD. When I run the recovery console and open a command prompt, I change to C drive and then dir and find that my VHD file is present instead of the Windows directories that are present inside the VHD image. I can use Diskpart to assign a different drive letter to the physical disk and to assign drive letter C to the VHD, which is where the Windows files are, and exit Diskpart and find that C drive looks like a normal windows boot disk. Then BCDBoot can be used to set up the boot. I tried this a few different ways, assigning for example drive letter F to the VHD, and then it should have booted, but the drive letter F was lost on reboot and it wouldn’t boot at all.

However on the other hand I did find this posting which tells me about a useful tool called wim2vhd which is produced by Microsoft and will make a VHD easily from a Windows install DVD. This appears to automate some of the manual steps listed in the walkthrough. Another post here gives more useful info. Right now, though, I am stalled until Technet can give me a way to make the drive letter assignment stick. Here is some more info on how to sysprep a VHD so that it can be copied to another machine. I plan to sysprep using MDT just to simplify things especially if we can automate driver injection in MDT.

Since first writing the above, it has been determined that the limitation is built into Window 7: attached VHDs are not automatically reattached at boot time unless required to boot an OS. I guess this could be because of a performance effect on startup. However, I think that Windows should provide support for turning on automatic reattachment as I can see a scenario that would be attractive is to have a data VHD as well as a OS VHD in place of physical disk partititions. Fortunately others have recognised this need and have addressed it with software and scripts (here’s another post suggesting how to set up as a scheduled task). My preference would be the free software, if it is free, followed by the Powershell script (which automatically scans and attachs all VHDs in a folder). This puts pressure on MS to include this feature in subsequent editions of Windows.

I am now working on a new VHD creation at home in my free time, the first step is to upgrade my PC from Pro to Ent. Also here I commend the addition of various useful features to later editions of 7-Zip, a free zip archiver. The latest release edition 4.65 can open and extract ISO and WIM files, and the development beta 9.14 can open and extract VHD files. So I didn’t have to buy software to get stuff out of an ISO file, and you don’t any longer have to mount a WIM in ImageX to get stuff out of it. The VHD functionality is mainly of benefit on older versions of Windows that don’t incorporate VHD attachment (i.e. versions prior to 7).