How to boot into bootable differencing vhdx in Hyper-V

Hello,

I am trying to upgrade my boot to VHD VHDX to the latest Windows 10 update using this terrific tutorial from @Kari: Native boot Virtual Hard Disk - How to upgrade Windows

However, I am having trouble getting the vhdx to boot in Hyper-V. Everything seems to work as expected, but when I get to step 1.18, Hyper-V gives a "The boot loader did not load an operating system" error booting off the VHDX.

I wonder if the boot files are getting created appropriately. When I run

c:\windows\system32\bcdboot c:\windows /s c:

it says it worked correctly, but if I run

bcdedit /v

after that, it says "The boot configuration data store could not be opened. The requested system device cannot be found."

The c: drive is available via the windows installation command prompt.

Other possibly useful information:
- The VHDX is a differencing disk, and the parent VHDX file is read-only
- The VHDX was created in Windows and initialized for Windows install using DISM. It was not created in Hyper-V.

Any ideas? Thanks in advance.

herg39458 said:

Hello,

I am trying to upgrade my boot to VHD VHDX to the latest Windows 10 update using this terrific tutorial from @Kari: Native boot Virtual Hard Disk - How to upgrade Windows

However, I am having trouble getting the vhdx to boot in Hyper-V. Everything seems to work as expected, but when I get to step 1.18, Hyper-V gives a "The boot loader did not load an operating system" error booting off the VHDX.

I wonder if the boot files are getting created appropriately. When I run

c:\windows\system32\bcdboot c:\windows /s c:

it says it worked correctly, but if I run

bcdedit /v

after that, it says "The boot configuration data store could not be opened. The requested system device cannot be found."

The c: drive is available via the windows installation command prompt.

Other possibly useful information:
- The VHDX is a differencing disk, and the parent VHDX file is read-only
- The VHDX was created in Windows and initialized for Windows install using DISM. It was not created in Hyper-V.

Any ideas? Thanks in advance.

Hi there

You can try this method (from the Ms documentation) which doesn't need HYPER-V features so should work on any Windows version.

https://docs.microsoft.com/en-us/win...-the-boot-menu

Cheers
jimbo

jimbo45 said:

Hi there

You can try this method (from the Ms documentation) which doesn't need HYPER-V features so should work on any Windows version.

https://docs.microsoft.com/en-us/win...-the-boot-menu

Cheers
jimbo

Thank you for the link. I am not having trouble creating or booting into a VHDX, I have been doing that without issue for a long time. The problem, which I should have been clearer about, is that you cannot upgrade Windows feature updates when booted into the VHDX, eventually Windows install just says "Bootable VHDs cannot be upgraded" or something like that. Hence the Hyper-V workaround in the aforementioned link.

herg39458 said:

Thank you for the link. I am not having trouble creating or booting into a VHDX, I have been doing that without issue for a long time. The problem, which I should have been clearer about, is that you cannot upgrade Windows feature updates when booted into the VHDX, eventually Windows install just says "Bootable VHDs cannot be upgraded" or something like that. Hence the Hyper-V workaround in the aforementioned link.

Hi there
OK understand now !!!
Cheers
jimbo

Circling back here after a few weeks, in case anybody else comes across this.

My apparent problem was I had a GPT VHDX without the appropriate partitioning configuration. I tried a number of solutions to get around this, but what I ended up doing was creating a new MBR VHDX with the appropriate partitions, restoring an image onto that VHDX, and doing the upgrade as directed in the upgrade post using Hyper-V.

More specifically:
- Create a new Gen-1 VM in Hyper-V, creating a new VHDX that is the same size as the VHDX that needs to be upgraded
- In the VM, point the virtual drive the Windows 10 ISO and boot it
- In Windows setup, get the point where you have to initialize and format the disk; do a format, then close setup. This is just to get the VHDX partitioned and formatted correctly. You should have a MBR VHDX with a system partition and data partition.
- turn off the VM

Next, image the new VHDX
- Since I was using a differencing VHDX, I was not sure mounting the drive and taking an image would work, so I booted into the VHDX I wanted to image.
- Using Macrium Reflect, I took an image of the running system
- Mount the new MBR VHDX, and restore the image as described here: Restoring a UEFI/GPT System image to MBR - KnowledgeBase - Macrium Reflect Knowledgebase

- Boot into the MBR VHDX to make sure everything is still working, which it was for me. If so, follow the instructions in the aformentioned tutorial.

I started with a differencing GPT VHDX and ended with a MBR VHDX that does not have a parent, so it was not a perfect upgrade. But for my uses, this was an acceptable trade-off, especially since the alternative was not upgrading Windows at all.

Hopefully that helps. Sorry for no screenshots.