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FAT32 bug in RMPrepUSB (not grub4dos)!


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#1 steve6375

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Posted 20 March 2013 - 12:47 PM

[Edit] This is NOT a bug in grub4dos!!! It is a bug in RMPrepUSB FAT32 formatting! Now fixed in v2.1.661.[/Edit]

 

I have a few USB pens formatted as FAT32 and I often place ISO files in the root just to quickly test them. Suddenly I found that grub4dos would not list some files that I just added on one of them! The new files are there in Windows Explorer but not under grub4dos. Even if I deleted some files from the root and then added a new file to the root again it was not listed.

 

I have noticed peculiar issues like this in the past and had to reformat the USB drive to fix it. 

 

I have reported this as a bug here.

 

To demonstrate this try making a new FAT32 USB flash drive with RMPrepUSB - installing grub4dos and then run this .cmd file from your Windows console

 

set USB=H:
set a=0

:LOOP
set /a a=a+1
echo t > %USB%\%a%.txt
if "%a%"=="130" goto :P
goto :LOOP

:P
del %USB%\126.txt
del %USB%\125.txt
del %USB%\124.txt
copy %USB%\1.txt %USB%\NEW1.txt
copy %USB%\2.txt %USB%\NEW2.txt
copy %USB%\3.txt %USB%\NEW3.txt

 

Now boot to grub4dos and do  ls /     - you should see that the NEWx.txt files are not listed, nor are any files above 126.txt!

 

If you often add/delete files from the root of a grub4dos FAT32 drive, you may find a similar issue.

 

Can someone confirm this bug please?



#2 steve6375

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Posted 20 March 2013 - 01:00 PM

Just tested FAT16 and it seems OK in FAT16!



#3 steve6375

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Posted 20 March 2013 - 01:09 PM

Interesting - if I re-format using Windows FAT32, then the problem does not arise.????

I wonder why???



#4 Wonko the Sane

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Posted 20 March 2013 - 01:51 PM

Interesting - if I re-format using Windows FAT32, then the problem does not arise.????

I wonder why???

Somehow it means that the RMPREPUSB USB formatting is *somehow* different from the built-in Windows one (BTW which Windows? Though I don't think there are differences in FAT32).

 

Could it be related to the "optimization" offsets? :dubbio:

 

:cheers:

Wonko



#5 steve6375

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Posted 20 March 2013 - 02:00 PM

An old version of RMPrepUSB (1.9.75) has the same issue.

I changed the partition type from C (RMprepUSB) to B (win) and still same issue.

I changed text in PBR from MSDOS 5.1  (rmprepusb) to 5.0 (win) still same issue.

Attached Files



#6 steve6375

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Posted 20 March 2013 - 03:33 PM

must be long-standing bug in RMprepUSB FAT32 procedure - I will work on it!



#7 steve6375

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Posted 20 March 2013 - 06:29 PM

 After making the BPB parameters and sectors 1-3 of the PBR identical the still occurred!

Clearly the issue was after the BPB.

I eventually traced it to the first 3 cluster entries!!

 

On a volume formatted by Windows these were:

F8 FF FF 0F    FF FF FF 0F   FF FF FF 0F

on an RMPrepUSB formatted volume they were:

F8 FF FF FF   FF FF FF FF   FF FF FF FF

 

this apparently caused the problem!!??

 

This now fixed in 2.1.661 which will be available shortly!






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