Date: Tue, 22 Oct 1996 13:19:47 +0200 (MET DST) From: Robert Eckardt <roberte@mep.ruhr-uni-bochum.de> To: grog@lemis.de (Greg Lehey) Cc: dgy@rtd.com, questions@FreeBSD.org Subject: Re: Making a DOS Partition writeable Message-ID: <199610221119.NAA13067@ghost.mep.ruhr-uni-bochum.de> In-Reply-To: <199610220915.LAA00686@freebie.lemis.de> from Greg Lehey at "22. Oct. 96 11:14:46"
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> Don Yuniskis writes:
> > It seems that Doug White said:
> >>
> >> On Mon, 21 Oct 1996, Snob Art Genre wrote:
> >>
> >>>> Please, anyone correct me, but mounting a DOS-FS could -- under certain
> >>>> circumstances -- corrupt the BSD-FS !?!?
> >>>
> >>> Shortly after I installed FreeBSD, I was running two finds on different
> >>> virtual consoles, with /msdos mounted, and my machine crashed hard. When
> >>> it came back up, my entire FreeBSD installation was hosed. I can't say it
> >>> was definitely due to msdosfs, but I suspect it.
> >>
> >> The primary problem comes when you FIPS a partition and cause the cluster
> >> size to change. FreeBSD assumes a perfect world while FIPS cheats -- it
> >> SHOULD rewrite all those sectors back down to the smaller clustersize but
> >> that takes a while (I had a program that actually did it right!) esp. on
> >> big disks.
> >
> > So, how does this result in the F-BSD partition being trashed? Or, is that
> > an "ugly rumor"? Is it only applicable to a F-BSD partition on the same
> > physical device as a FIPS'ed DOS partition? etc.
> >
> > It sure would be nice if these things were more thoroughly described or
> > qualified ... help reduce some of the "lore" surrounding them.
>
> Good question. I've been holding back, since I don't use MS-DOS or
> its file systems, but my understanding was that FIPS leaves some
> pointers in the file system pointing outside the partition. I'd guess
> that the FAT is a good candidate here, since you can't shrink it
> easily. This doesn't seem to worry the native MS-DOS file systems (or
> I just haven't heard of it happening), but apparently it can cause
> FreeBSD's msdosfs to write outside in the area which belonged to the
> file system before it was truncated with FIPS. In the kind of
This doesn't explain to me, why mounting a DOS-FS would corrupt the BSD-FS
when I do *not* write to the DOS part.
Just reading, using find or simply mounting (and I remember vaguely that
the mount itself could destroy it) should not cause problems !???
(some data structures overwritten in the kernel ?)
As far as I see it from several mails that I have received on my question,
i) using plain DOS with fdisk to create the DOS partition and leaving
space for another OS is (perfectly) safe.
ii) Using Win95 or WinNT progs for partitioning *may* cause problems
with the partition table and/or the DOS-FS (even w/o FreeBSD).
iii) Using FIPS -- as was noticed on these lists several times -- will
almost certainly cause problems.
These `problems' may end up in the worst case in crashing the BSD-FS
(which I don't understand).
Since my system falls in category i) I saw never problems with it.
I'm afraid that the only `testing' will be `failed installations' of
cat. ii) and iii). There may, however, something else have went wrong.
Finally, esp. when installing a new OS, I like to quote Larry:
"Save often, save early !"
> situation we're looking at, where FIPS was used to make space for a
> FreeBSD file system, this will now be a FreeBSD file system. That's
> plausible, but I haven't personally seen any evidence that it has
> happened. If somebody else has, please speak up.
>
> Greg
Just my contribution to the general confusion :-)
Robert
--
Robert Eckardt \\ FreeBSD -- solutions for a large universe.(tm)
RobertE@MEP.Ruhr-Uni-Bochum.de \\ What do you want to boot tomorrow ?(tm)
http://WWW.MEP.Ruhr-Uni-Bochum.de/~roberte
For PGP-key finger roberte@gluon.MEP.Ruhr-Uni-Bochum.de
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