[Bug 463015] Re: Both fat and ext[234] boot sectors present at once cause confusion

[Theodore Ts'o]

Ok, so I've taken a closer look at this.

mke2fs *does* zap the first 1k of the file system (by writing all
zeros).  The only system where it doesn't do this is sparc, because
apparently that seriously screws up the bootloader.  I don't remember
the details, only that the sparc folks were screaming at me about it.

Looking at the blkid probes at least, it always checks various offsets
in the first 1k of the file system, and so this is enough to prevent
blkid from getting confused.   I don't know what grub is doing, but I
consider that a potential grub problem, and not mine; if blkid does the
right thing, and other programs are getting confused, then maybe they
should just use the blkid library.  :-)

Anyway, I don't have more time to look at this, but as near as I can
tell mke2fs is doing the right thing.  If someone disagrees, they need
to specifically give me a request about what mke2fs should do
differently.

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https://bugs.launchpad.net/bugs/463015

Title:
  Both fat and ext[234] boot sectors present at once cause confusion

Status in “e2fsprogs” package in Ubuntu:
  New
Status in “grub2” package in Ubuntu:
  New

Bug description:
  Binary package hint: grub2

  grub-probe incorrectly identifies my ext3 partition as containing a
  fat file system.  This means it can't boot without manual tweaking.

  I suspect the problem is that my partition contains stale fat
  signatures... this is probably a common problem, as mke2fs often
  doesn't wipe old signatures.

  I attached first 8k of my file system for testing purposes.

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