Booting OS from a single VHD file offers plenty of advantages in many usage scenarios. Win7 Bootldr supports native OS boot from VHD via a native VHD driver, whether the VHD is fixed, dynamic or differencing, whether contiguous or not. Its a tremendous advantage over current Grub4DOS state, supporting only boot from fixed contiguous VHDs. However, the disclosed so far by MS way to boot OS from VHD requires a supported OS version (Win7 Ultimate / Enterprise & Server 2008R2), while Grub4DOS can boot just about any OS from VHD, when a mapped by Grub4DOS VHD can be hot-swapped by a pre-installed to the OS on VHD 3rd party VHD driver. The boot process follows conditions stored in BCD Store Registry hive.
The challenge is: how to change parameters of Win7 BCD Store installed on a host drive to make Bootmgr on the host chainload Bootmgr on a VHD saved on that host? Or chainload any other bootloader inside that VHD?
That way one would be able to use native Bootmgr support for all VHD types, while also overcoming OS version restrictions, since when OS is booted by a boot device located inside the VHD, it considers that drive to be a Hard Drive, and not a VHD, hence boot restrictions are lifted.![:secret:]()
Of course, a separate challenge would be to teach a 3rd party VHD driver installed to the OS on VHD to hot-swap the virtual drive, mapped by Bootmgr, or to port native VHD drivers to Legacy OSs, but at least all Win7 versions will get supported for native boot that way without any restrictions. Keep in mind so, this is a learning challenge, not intended to bypass any OS licensing terms, but to improve your knowledge and skills in the OS Boot subject. Don't use any such method for daily computing tasks!![:)]()
To help, there are several tools available to manipulate BCD Store content, some more convenient are EasyBCD and Visual BCD Editor. Of course, Virtual Hard Disk Format Specification and BCDEdit Commands for Boot Environment can help, also BCD WMI Provider Reference. Don't forget to also look through Diddy's BCDEdit Notes as well, and use Boot Configuration Data Tutorial if not satisfied. Some extra info is also found in How to edit BCD with Editor forum thread, and plentiful other sources on the web.![:pizza:]()
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When playing with VHDs, one can accidentally mount 2 of them with the same OS cloned, thus prompting the system to change Disk Signature on one of the VHDs. EasyBCD can fix that with BCD Deployment feature, once you open a suitable BCD Store in it from any running OS. Another way of Fixing Disk Signature Collisions outcome, blocking OS boot from VHD, would be manually reverting back its original Sig. Keep in mind however, Disk Signature seems to be only verified when chainloading control to a bootloader inside the VHD, i.e. when treating it as a Hard disk rather than Filedisk.![:wub:]()
Good luck with your efforts, and keep members posted on your success.![:)]()
The challenge is: how to change parameters of Win7 BCD Store installed on a host drive to make Bootmgr on the host chainload Bootmgr on a VHD saved on that host? Or chainload any other bootloader inside that VHD?
That way one would be able to use native Bootmgr support for all VHD types, while also overcoming OS version restrictions, since when OS is booted by a boot device located inside the VHD, it considers that drive to be a Hard Drive, and not a VHD, hence boot restrictions are lifted.
Of course, a separate challenge would be to teach a 3rd party VHD driver installed to the OS on VHD to hot-swap the virtual drive, mapped by Bootmgr, or to port native VHD drivers to Legacy OSs, but at least all Win7 versions will get supported for native boot that way without any restrictions. Keep in mind so, this is a learning challenge, not intended to bypass any OS licensing terms, but to improve your knowledge and skills in the OS Boot subject. Don't use any such method for daily computing tasks!
To help, there are several tools available to manipulate BCD Store content, some more convenient are EasyBCD and Visual BCD Editor. Of course, Virtual Hard Disk Format Specification and BCDEdit Commands for Boot Environment can help, also BCD WMI Provider Reference. Don't forget to also look through Diddy's BCDEdit Notes as well, and use Boot Configuration Data Tutorial if not satisfied. Some extra info is also found in How to edit BCD with Editor forum thread, and plentiful other sources on the web.
When playing with VHDs, one can accidentally mount 2 of them with the same OS cloned, thus prompting the system to change Disk Signature on one of the VHDs. EasyBCD can fix that with BCD Deployment feature, once you open a suitable BCD Store in it from any running OS. Another way of Fixing Disk Signature Collisions outcome, blocking OS boot from VHD, would be manually reverting back its original Sig. Keep in mind however, Disk Signature seems to be only verified when chainloading control to a bootloader inside the VHD, i.e. when treating it as a Hard disk rather than Filedisk.
Good luck with your efforts, and keep members posted on your success.