How to tell Windows Boot Manager (bootmgr) to load and execute the 1st sector from a specified partition?

G

Goerge255

New Member
I have 2 old-style MBR partitions (non-GPT):

  1. An "active" partition containing `Windows 7 OS` and its `bootmgr` - the Windows Boot Manager and its BCD..
  2. The second partition contains an exotic non-Windows OS, which has its own bootloader code in its Partition Boot Record (PBR/VBR) - the 1st sector of the 2nd partition (512 bytes).

I can successfully boot the Exotic OS through the Windows7's Boot Manager (bootmgr) by creating a Boot Menu entry with the following steps:

Code: 
    Copy the first sector of the Exotic OS' partition into the file named `exotic.bin` in the Windows7's filesystem.
    Execute:
         bcdedit /create /d ExoticOS /application bootsector
         bcdedit /set {**guid**} device partition=c:
         bcdedit /set {**guid**} path \exotic.bin


However, this method of booting is imperfect because the Exotic OS often updates its own boot sector (in the 1st sector of its own partition) and then the file `exotic.bin` becomes outdated.

QUESTION: How to instruct the Windows Boot Manager (bootmgr) to load & execute the Exotic OS' boot sector, DIRECTLY from the 1st sector of the 2nd partition - not from the outdated copy `exotic.bin` ?
 
You can't do that because the bootloader is executed in an environment a level up from the BIOS and has abstracted away the disk and drive access, instead using local paths only.
My recommendation would be to write a simple script and add it to the Task Scheduler that updates exotic.bin each time you log into Windows.
 
Alternatively, and this is what EasyBCD does internally for some entries, you can add a NeoGrub entry and configure that to chainload into hd(x, y) in which case NeoGrub will be loaded from a static file on-disk that doesn’t change but it will dynamically chainload your exotic OS from its real-time partition boot sector.
 
Back
Top