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From: Marcos Mello <marcosfrm@gmail.com>
Subject: Re: Placing the root partition on an XFS filesystem is not supported
Date: Mon, 6 Feb 2012 10:44:07 +0000 (UTC)
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Eric Sandeen <sandeen <at> sandeen.net> writes:

> On 2/5/12 7:54 PM, Dave Chinner wrote:
> > On Sun, Feb 05, 2012 at 06:13:28PM -0600, Eric Sandeen wrote:
> >> On 2/5/12 6:11 PM, Dave Chinner wrote:
<snip>
> >>
> >> well, it was worse than that.  I can work around the grub-on-a-partition
> >> problem, but what I ran into was grub reading & writing to/from the block
> >> device under a mounted filesystem - corruption and hilarity ensued.
> > 
> > Oh, grub2 does worse things than that - grub_probe mounts any device
> > that appears to have a valid superblock so it can find out what
> > devices it needs to list in it's boot menu. I found this out when I
> > built a big DM stripe out of disks that used to have filesystems on
> > them.  grub-probe mounted every single device -inside- the stripe
> > and ran log recovery on them, corrupting the new filesystem and
> > quite a bit of data on the DM stripe they were part of....
> 
> Ok, your horror story wins from a pain POV ;)
> 
> but sounds like someone should have zeroed out a bit more disk
> when setting up the dm stripes :(
> 
> I've always thought maybe we needed a libzero.so to zap every known signature
> on disk....
> 

Thanks a lot for the explanation folks! It would be nice have this documented on
the XFS FAQ
http://xfs.org/index.php/XFS_FAQ#Q:_Does_GRUB_work_with_XFS.3F

Eric, landed recently in util-linux's libblkid a function for that AFAIK
http://git.kernel.org/?p=utils/util-linux/util-linux.git;a=commitdiff;h=2b89be6c802bdbdf6830dbd060c96e33f179b135

Marcos