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!

Structure com.vmware.appliance.recovery.backup.job.details.info has a union with a field not required for this case = end_time

A VCSA 6.7 backup may fail with this error.  The most common explanation is that this is related to file permissions as described in this article.  But what if you're not using an IIS ftp server?  I was testing this using FileZilla FTP Server on Windows 10 1809.  In my case the service was running as SYSTEM, which already had full access to the FTP directory.  In fact it was creating subdirectories, but would fail when attempting to upload a file.

What I discovered was that the VCSA uses passive mode FTP with no option to change that fact.  By default passive mode servers choose random ports >1023 and pass them to the client which will then open a data connection to that port as described here. Unfortunately the Windows Firewall on this machine was set in the correct restrictive fashion, so those passive mode ports were never permitted.

It is possible, however, to choose custom passive mode ports in FileZilla.  In the server settings I chose to use the range 1024-1048, and then whitelisted those same ports in the firewall.  After that the backup completes successfully.