Message-ID: <3C42BE0E.2090902@namesys.com>
Date: Mon, 14 Jan 2002 14:16:30 +0300
From: Hans Reiser <reiser@namesys.com>
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To: Oleg Drokin <green@namesys.com>
CC: reiserfs-list@namesys.com, linux-kernel@vger.kernel.org,
        ewald.peiszer@gmx.at, matthias.andree@stud.uni-dortmund.de
Subject: Re: [reiserfs-list] Boot failure: msdos pushes in front of reiserfs
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Oleg Drokin wrote:

>Hello!
>
>On Sun, Jan 13, 2002 at 11:38:03PM +0100, Matthias Andree wrote:
>
>>3. I presume that msdos is linked into the kernel, and is thus tried
>>   first as root file system, the kernel then panicks as it cannot find
>>   /sbin/init (of course, it's in ReiserFS format, not msdos).
>>
>It is tried _and_ somewhat succesfuly, because there is still MSDOS "superblock".
> 
>
>>4. I asked Ewald to boot with rootfstype=reiserfs, but he reported that
>>   this did not help, news:<a1sb7b$t2d2e$1@ID-47183.news.dfncis.de>
>>   (German-language).
>>
>Hm, probably because reiserfs is not in kernel, but is an external module.
>
>>5. It seems as though some traces of FAT16 shining through reiserfs
>>   still make msdos think it can actually mount the file system.
>>
>Exactly.
>
>>I see various points where this can be attacked:
>>1. SuSE and other distributors' installation tools, when formatting a
>>   partition with mkfs, should zero out the first couple of MBytes with
>>   dd if=/dev/zero of=/dev/hda13 bs=4096 count=1024 or something. I'm
>>   not exactly sure how much is needed to get rid of the msdos traces.
>>
>Erasing first 512 bytes block is enough to get rid fo msdos superblock, I think.
>
>>2. mkreiserfs could also zero out so much of old data on the FS so that
>>   the kernel reliably recognizes the FS as reiserfs and fails to mount
>>   that stuff as msdos
>>
>External tools (lilo and stuff) can live there, this will destroy them.
>
>Correct solution, if you create filesystem with mkreiserfs, and you
>have no reliable way to pass fstype to kernel, when this partition is mounted 
>should be to destroy all occurences of other fs's superblocks by yourself, obviously.
>
>>3. Distributors, when making their initrd stuff, should make sure that
>>   all Linux-native file systems are tried first.
>>
>FS tryout order is hard-wired into the kernel (and depends on linking order, AFAIK).
>
>>Ewald has only recently migrated from Windows to Linux and direly wants
>>his installation to boot. For now, I asked him to recompile his kernel
>>to let msdos, umsdos and vfat be only modules rather than linked into
>>the kernel, rebuild his initrd with SuSE's mk_initrd and rerun lilo,
>>that should work around his problem, but it's certainly not good and may
>>turn away people from Linux who are less enduring and patient than
>>Ewald.
>>
>why have not you asked him to do 'dd if=/dev/zero of=/dev/his_partition bs=512 count=1'?
>(and this won't destroy existing reiserfs filesystem).
>
>Bye,
>    Oleg
>-
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>
So what solution should we use, zeroing or fixing msdos to not try 
something reiserfs can find, or both or what?

I want the solution to also fixes the error messages from msdos that it 
issues when it sees reiserfs that are confusing for users.

Hans


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