Special FAT filesystem questions [Was: Multiple files with same filename on FAT]

Vicne · 2007-11-06T23:02:28+00:00

Hi,I'm still in the process of understanding the special FS my PVR uses(see "Multiple files with same filename on FAT" thread a few daysago).I read the spec of the MBR and BootSector / BPB, and manually walkedthrough these parts.I can see that the first (and only) partition is declared the standardway as a 16-bit FAT (06h) in the MBR.Although, the boot sector of this partition clearly corresponds to aFAT32 (with a few weird values in reserved fields, but well). The lastfield (filesystem type) even reads "FAT32 ".I have a few questions though regarding the FAT itself (the actuallinked list), that I'd like to submit to specialists (that'syou :-)) :- Can anybody explain me how to determine where the FAT starts on thedisk ?- Does anybody have an idea what the following structure is :The first non-zero sector I find after the BS is at BE00h (offset inbytes from start of disk) and looks like some kind of linked list on24 (!) bits, stuffed with FF as fourth byte, like this :FF FF 1F 09 FF FF 1F FF 04 00 00 FF FF FF 1F FFDF 07 00 FF FF FF 1F FF 07 00 00 FF 08 00 00 FF0A 00 00 FF FF FF 1F FF 0B 00 00 FF 0C 00 00 FF0E 00 00 FF FF FF 1F FF 0F 00 00 FF 10 00 00 FF11 00 00 FF 12 00 00 FF 13 00 00 FF 14 00 00 FF15 00 00 FF 16 00 00 FF 17 00 00 FF 18 00 00 FF...(and there's a copy of it starting at 31200h)I guess it's not the FAT yet, right ?A few bytes after the end of the that copy (at 56800h precisely), whatI think is the actual FAT begins, like this :81 00 00 00 82 00 00 00 83 00 00 00 84 00 00 0085 00 00 00 86 00 00 00 87 00 00 00 88 00 00 0089 00 00 00 8A 00 00 00 8B 00 00 00 8C 00 00 00...(and there's a copy of this one starting at 12F6200h)Any hint or information is welcome, of courseVicne

Nov 06, 2007 24 Replies

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Vicne 18 years ago

Noted. Thank you for the explanations.

I think I'll only be able to test that next week-end though.

Thanks again.

Vicne

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Gene S. Berkowitz 18 years ago

The latest Ubuntu distro found my NTFS partition out of the box, er, download...

--Gene

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Vicne 18 years ago

Downloading right now. Can you just confirm it's mounted read/write ? Thanks.

Vince

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Gene S. Berkowitz 18 years ago

Yes, it mounts r/w:

File System: ntfs (3.0) / fuseblk Mount Options: rw nosuid nodev noatime

--Gene

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Anton Erasmus 18 years ago

Both Knoppix and Ubuntu ar debian based distributions. Knoppix mounts existing partition as read only as a safety feature. It is trivial to remount read/write using the normal GUI tools.

If you are getting Ubuntu, make sure you are getting the LiveCD version. Otherwise you will have to install it, and make your machine dual boot before you will be able to use it.

Regards Anton Erasmus

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