Booting from Virtual disks - both Windows / Linux - which bootloader are best for it?

[ruthan]

Hello,
i have tried to research booting from vhd, it could be practical, but so far my results are not great.

 I expected to find much more articles about it.

1) Windows 7+ BCD - its its working, but its limited
 It seem to be limited to Windows 7 or maybe Vista. Later Windows 10/11 are probably able to boot Windows 7+ machines, but its not possible to boot Linux from vhd.
   Problem is also how to create VHD for it:
 a) Because tutorial are quite long im not sure if possible to install Windows from live Windows session to some VHD. 
b) People are used to create VHD through some virtualization software, but there is after problem that physical HW is different that real hardware.
  I managed to connect virtual disc in Windows and use Paragon HW P2P adjust to add real storage drivers to make it bootable, but its commercial products and it seems that from more modern versions P2P adjust from live Windows sessions for other partitions where removed.
    There is some old 2010 version with P2P adjust for the live Windows session.. Because connecting VHD from WINPE or Linux based boot disk, not working or its complicated.
    Yeah can install Windows on physical partitions convert it to vhd image and delete original partition, but it needs possiblity of live install or some enhanced OS installer which is able to connect VHD as installer target partition - im not sure if it exist, again Paragon has some OS migration tools and there are some OS migration tools from other companies too - some proven tips for them would be great.

Ventoy USB loader, has optimal Windows 7 / 10 /11 plugin too, but egain you have to adjust VHD for real HW boot.
Hyper-V machine probably can be booted from Windows 10/11 bootloader.

2) Plop VHD loader
its from 2010 - https://www.plop.at/en/vhdloader.html not more updates, it needs FAT32 partition on the same disk from its executed (it cant find vhd on other disks - i have tried it).. im able to run it from Grub2Dos, but i have tried to run NT4 vhd - vhd file is found, but not even reached Windows logo, i will try other OS images later, im not sure if this not dead end.
   Fat 32 mean that is limited only to max - 4 GB virtual disk, fixed and dynamic disk image sizes are support, but im not sure what will happen when dynamic disk size would try to get bigger than 4GB.. Vmware can split vhd into multiple fixes, but i doubt that is supported by this bootloader.
  Update: i 1 tested like 10 Pcem (86box) vhds with old oses, but even OS inside virtual disk has to be FAT32.. I often get classic erros like invalid disk or missing operating systems, i only managed to get Win3.11+MS-DOS 6 vhd to get futher than booting message.. i get MS-DOS started, after some config execution error.. so no config commands processed, afte that i got into command line, dir / cd worked, but otherwise wrong data i subdirectories and execution tools like edit failed, win.com failed too.. for some valid command i got invalid command. I have to check it, but it seems that these vhds where FAT16 not FAT32.
   It seems that very specific vhd disk format version is supported, in project description are not details, only info that dynamic size is suppoted too. Maybe *.vhds are too new for 2010 tool. Im not even sure if there is vhd format downgrade too (i prefer GUI based one).
  My vhds, where no stored at Win98 FAT 15GB partition, second after 15 NTFS - NT4 partition, on 500 GB Sata disk (in ATA mode in Dell server Bios, i guess that means IDE PATA mode, because disk is visible by Windows 98 CD-Rom command line and Window 98 start up floppy disk.

3) Grub 1 (Grub4dost) / Grub 2 
So far im failing to find good tutorial for Grub 1 / Grub 2 vhd booting, i found some supposed success stories, but they often lack some important details. 

4) Yeah i know that are bare metal virtualizer as ESX, Unraid, which are using virtual disks, but its something else, that add some vhd boot to existing machine setup - yeah i know i could simply create some Unraid physical disk and use special BIOS / EFI entry to it and kept existing normal booting  machine untouched, its not quick or easy to setup how configuration.

Edited May 28 by ruthan