Migrate a Centos 7 VM from VirtualBox to Hyper-V

Recently I decided I wanted to install Docker Desktop for Windows in order to do some local testing.  The installation process is pretty straightforward but requires Hyper-V be enabled on the machine.  This is automatically done by the installer, but contains one minor inconvenient caveat: once Hyper-V is enabled, VirtualBox no longer functions.  My understanding for this is that Hyper-V is a ring-1 hypervisor which runs your primary OS as an (albeit special) VM.  Because of that, it's no longer possible to run a ring-2 hypervisor like VirtualBox.

There's plenty of guides out there on how to make this migration, but they all seem to be missing at least a few important points.  For the most part I followed this guide which has links to all of the required tools.  Here's the list of issues that I faced that were not covered in that article:

1. Convert-VHD would not recognize by vmdk file.  Ultimately I ended up finding this article which proposed an alternate command: ConvertTo-MvmcVirtualHardDisk. This worked as described in the original article.

2. The original article is a little vague on which lines might need to be commented out in the "desc.txt" file that is created.  I ultimately ended up needing to comment out these:

#ddb.uuid.image="8ce66459-16da-4a18-a56b-6149a49e0de3"
#ddb.uuid.parent="00000000-0000-0000-0000-000000000000"
#ddb.uuid.modification="00000000-0000-0000-0000-000000000000"
#ddb.uuid.parentmodification="00000000-0000-0000-0000-000000000000"

3. Once those issues were resolved, I had a new vhdx that I was able to attach to a new Hyper-V VM.  Unfortunately it wouldn't boot.  On a normal boot the VM would hang at the graphical boot screen for a few minutes, then fail and dump to the dracut recovery shell.  A look at journalctl indicated that this was because none of the disks were found.  A lot of articles on this issue recommend rebuilding the initramfs by rebooting and choosing the "rescue" option on the GRUB boot menu.  I did find that the rescue option would boot, but unfortunately rebuilding initramfs with: dracut --force didn't seem to have any effect.  Luckily the nice folks on freenode IRC #centos pointed me in the right direction:  my virtualbox VM had the guest additions installed still!  This article explains how to remove the vbox guest additions, but basically just run the installer again with the uninstall argument:

sudo sh /media/VBOXADDITIONS_4.1.10_76795/VBoxLinuxAdditions.run uninstall

Obviously hyper-v has no menu item to mount the guest additions CD, but the .iso can be found at:

C:\Program Files\Oracle\VirtualBox\VBoxGuestAdditions.iso

Once that was uninstalled, one final reboot and... bob's your uncle!