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Re: grub-probe fails to find PC partition due to Apple disklabel

From: Chris Knadle
Subject: Re: grub-probe fails to find PC partition due to Apple disklabel
Date: Mon, 28 Jul 2008 14:41:29 -0400
User-agent: KMail/1.9.9

On Sunday 27 July 2008, Felix Zielcke wrote:
> Am Freitag, den 25.07.2008, 19:09 -0400 schrieb Chris Knadle:
> >    Just tested -- nope, grub-probe still can't find the device.
> >
> > So this:
> >
> >    kern/partition.c:106: Detecting apple_partition_map...
> >    kern/disk.c:368: Reading `hd0'...
> >    partmap/apple.c:129: bad magic (found 0xfc31; wanted 0x4552
> >    kern/partition.c:112: apple_partition_map detection failed.
> >
> > means that this patch is trying to match the HFS magic number on the
> > first sector of the drive, when that doesn't have a filesystem magic
> > number at all.
> kern/partition.c:117: pc_partition_map detection succeeded.
> Just after the snippet you wrote.
> So I think it should work.
> Maybe you didn't test this right?

   I went back and looked at the bug report again.  Early on Robert suggested 
removing Apple partition detection, after which 'grub-probe -d /dev/hde2' 
succeeds (ext2).  [It's not in the bug report, but 'grub-probe -d /dev/hde3' 
also succeeds (xfs)].  So I'm satisfied that at least the overall testing 
method is fine.

   However on the last test I did make an error and left out the -d option to 
grub-probe, and that's required for the grub-probe to succeed, so 
unfortunately the output I posted is erroneous.
   A new one is attached which has Robert's patch applied -- it does succeed 
in finding the partition, but unfortunately we can't fix the problem this way 
because I believe it makes Apple partition detection *always* fail.

> Wipe a disk, then make an apple partition, and then make msdos
> partitions and make a filesystem on it.
> Just like it probable was as you reported the bug initially.

   Duplicating the problem is fine, but I don't see how this changes the 
testing method.  I'm probably willing to duplicate this on another system 
later, although independent verification would probably be better.  Right now 
I'm more interested in focusing on trying to remove Apple partmap detection 
for the PC architecture, since we already know that will fix the problem.

> Btw. I just read the whole story again and I was wrong saying that
> grub-legacy won't have a fix for this.
> grub-legacy now uses grub-probe so if grub-probe works then both are
> fixed for you.


   -- Chris


Chris Knadle

Attachment: apple-patch_partmap-detect.txt
Description: Text document

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