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Re: Bug#709097: grub-pc: Boot failure after updating to 2.00-14 - cannot


From: Vladimir 'φ-coder/phcoder' Serbinenko
Subject: Re: Bug#709097: grub-pc: Boot failure after updating to 2.00-14 - cannot find normal.mod, grub-rescue reports /boot empty
Date: Mon, 12 Aug 2013 11:54:44 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130630 Icedove/17.0.7

On 11.08.2013 15:53, Colin Watson wrote:
Control: retitle -1 misdetects FAT-overwritten-with-ext2 as FAT
Control: severity -1 important

This is a pretty specialised (hence the severity downgrade), but
interesting, corner case.  It appears that the partition in question
used to be a FAT filesystem (specifically, a Dell Utility partition).
It has been overwritten sufficiently that the fstype magic has been
overwritten:

   00000000  eb 54 90 00 65 6c 6c 20  38 2e 30 00 02 08 01 00  |.T..ell 
8.0.....|
   00000010  02 00 02 00 00 f8 86 00  3f 00 ff 00 3f 00 00 00  
|........?...?...|
   00000020  92 2a 04 00 80 00 29 1c  0a d9 07 44 65 6c 6c 55  
|.*....)....DellU|
   00000030  74 69 6c 69 74 79 00 41  54 31 36 20 20 20 10 00  |tility.AT16   
..|

How does something like that come into existence? Why would only part of BPB overwritten? The tools that I know either overwrite whole sector or don't touch BPB.
Vladimir, could you elaborate on this?  Which mkfs implementations were
involved here?

AFAIR it was some FAT images that are commercially distributed. AFAIR neither Windows nor Linux check this field.
It seems questionable to me for GRUB to be quite this liberal.  Perhaps
we can restore its previous strictness somehow without breaking the
filesystems that Vladimir ran into?

Thanks,





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