From: Karel Zak <kzak@redhat.com>
To: Phillip Susi <psusi@ubuntu.com>
Cc: util-linux@vger.kernel.org
Subject: Re: blkid doesn't find lvm pv when boot loader installed
Date: Mon, 14 Oct 2013 15:59:53 +0200 [thread overview]
Message-ID: <20131014135953.GG28914@x2.net.home> (raw)
In-Reply-To: <525821B6.9010304@ubuntu.com>
On Fri, Oct 11, 2013 at 12:05:10PM -0400, Phillip Susi wrote:
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> When installing a boot loader into an LVM PV, blkid detects it as a
> dos partition table and does not probe the lvm superblock.
Yes, unfortunately this is currently unsupported scenario.
The libblkid checks for collision between LVM and filesystems/partition
tables to avoid very common situations when users use whole-disks
previously used by LVM in new setups with partition tables.
Unfortunately, partitioning tools usually does not wipe LVM header
from the device and it easy to create situation when there is
valid PT as well as valid LVM header.
So.. libblkid assumes that there is only LVM header within first 8K
of the device, because pvcreate wipes this area (try pvcreate again
and it will silently erase your grub!). If there is anything else
then the previously detected LVM is ignored.
Yes, it's really not perfect solution, but do we have any better
solution? Maybe it would be enough to improve the blkid partition
table parser to not interpret the boot loader with empty PT as a
valid PT. Not sure.
Karel
--
Karel Zak <kzak@redhat.com>
http://karelzak.blogspot.com
next prev parent reply other threads:[~2013-10-14 14:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-11 16:05 blkid doesn't find lvm pv when boot loader installed Phillip Susi
2013-10-14 13:59 ` Karel Zak [this message]
2013-10-14 15:01 ` Phillip Susi
2013-10-18 9:36 ` Karel Zak
2013-10-18 11:57 ` Karel Zak
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