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From: Robert Nordier <rnordier@iafrica.com>
Message-Id: <199608241440.QAA00248@eac.iafrica.com>
Subject: Re: DOS root directory?
To: hackers@freebsd.org
Date: Sat, 24 Aug 1996 16:40:47 +0200 (SAT)
In-Reply-To: <199608241007.MAA09821@uriah.heep.sax.de> from "J Wunsch" at Aug 24, 96 12:07:17 pm
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J Wunsch wrote:
> 
> As Robert Nordier wrote:
> 
> > Most users with very large DOS filesystems probably do shrink them
> > when installing FreeBSD.  And if FIPS were more conscientious, it
> > would adjust the cluster size to something more appropriate (and
> > probably then <= 32 sectors).
> 
> This would require a complete reorganization of the file system, not
> just adjusting the BPB only.

Yes.  By "adjust the cluster size", I didn't mean (of course) just
adjust the cluster size value in the BPB.

There is a FIPS competitor, also freeware, called "Partition
Resizer", by John Lagonikas, which does shrink partitions correctly,
even changing FAT entry size between 16 and 12 bits, where necessary.

With more user awareness of what FAT filesystem mount code properly
entails, I think FIPS would probably have less of a following.

Consider this logic applied by MS-DOS to the "OEM Name & Version"
string in the boot sector BPB (quick 80x86 to C translation):

   if (!(oem[5] == '2' && oem[6] == '.' && oem[7] == '0')) {
      /* ... */
      if (oem[5] == '0' && oem[6] == '.') {
         /* ... */
         if (oem[4] != '1' && oem[4] != '2')
            disable_access_to_filesystem();
      } else if (oem[6] < '.' || oem[6] == '.' &&  oem[7] < '1') 
         derive_cluster_and_FAT_size_by_table_lookup();
   }

Too bad if my "format" utility sets bsOemName[6] != '.'; if even
a "harmless" virus uses the space for something; or if the boot
sector just gets partially corrupted.

-- 
Robert Nordier