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Different sizes of 'bootmgr' file (same iso)- what's the difference?


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#1 Atari800XL

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Posted 11 August 2016 - 09:30 AM

Short and sweet: can anyone explain the differences in

'bootmgr' (in the root of my Windows 10 iso)

end

'bootmgr' (in \sources\install.wim\1\Windows\Boot\PCAT\)

 

First one is 377 kB (386.976 bytes)

Second one is 375 kB (384.322 bytes)

 

For example, SIW2's PE scripts use the second one, but I don't understand why, extracting it seems more work than just taking the one from the root (as other projects do)? Makes me think there has to be a reason to use the second one?

 

I'm using this for USB booting on BIOS systems, just trying to learn how it all works, seems all I need for BIOS is BOOTMGR, \Boot\boot.sdi, \Boot\BCD and the boot.wim? Once again, just trying to learn, no problems with getting stuff to work or anything. Thanks!



#2 Wonko the Sane

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Posted 11 August 2016 - 10:53 AM

They might be slightly different versions, I wouldn't be surprised if the one in \sources\install.wim\1\Windows\Boot\PCAT\ is the actual "release" version and the one in root of the.iso is a previous one (or viceversa).

But - maybe - since the difference in size is around 2 Kb, is it not that you are confusing BOOTMGR (without extension and that includes a 16 bit stub, actually around 2 Kb in size) with BOOTMGR.EXE (the actual executable without the stub)? :unsure:

You could check if the tools for older versions still work:
http://reboot.pro/fi...mgr-recompiler/

But yes, to boot a PE, you just need a BOOTMGR, a \boot\BCD and a boot.wim, the \boot\boot.sdi is also needed as "mount point" for the wim but that is a "generic", "empty" NTFS filesystem that - JFYI - can be modified/reduced, another piece of good work by Joakim:
http://www.msfn.org/...ize-of-bootsdi/

:duff:
Wonko

#3 Atari800XL

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Posted 11 August 2016 - 11:22 AM

Yes, I read Joakim's "adventures" yesterday, very entertaining!!!

 

No, I didn't confuse bootmgr and bootmgr.exe (I think). They're both "bootmgr", and they both work.

 

Datestamps:

First one is 377 kB (386.976 bytes): 20160717 00:52:59

Second one is 375 kB (384.322 bytes): 20160716 13:43:00

 

See, I only recently learned that there was a difference in these files between *Windows versions* in the first place, as in: Older PE's boot with newer boot files, but newer PE's don't boot with older boot files. That's why I find it strange to find two different versions of 'bootmgr' on the same iso.

 

Once again: I'm just curious...



#4 Wonko the Sane

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Posted 11 August 2016 - 01:09 PM

Once again: I'm just curious...

Maybe not "curious enough" :w00t: :ph34r:
If you were really curious, you would have tried to strip the stub, uncompress the executable and - if successful - compared the executable properties/metadata (where possibly a build number could be found) :unsure:.


:duff:
Wonko




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