From: Phillip Susi <psusi@ubuntu.com>
To: Karel Zak <kzak@redhat.com>
Cc: util-linux@vger.kernel.org
Subject: Re: blkid doesn't find lvm pv when boot loader installed
Date: Mon, 14 Oct 2013 11:01:23 -0400 [thread overview]
Message-ID: <525C0743.9020706@ubuntu.com> (raw)
In-Reply-To: <20131014135953.GG28914@x2.net.home>
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On 10/14/2013 9:59 AM, Karel Zak wrote:
> 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.
Isn't mdadm in the same boat? i.e. you have a partitioned single
disk, and decided to turn it into a raid1. Now the partition table is
still there and valid, but should be ignored in favor of the raid
superblock.
> 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.
I started thinking along those lines, but it doesn't cover the above
mentioned raid1 case.
I'm now leaning towards thinking that any partition tool that doesn't
wipe the existing signatures is broken, and that's what needs fixed
rather than trying to work around it in blkid.
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next prev parent reply other threads:[~2013-10-14 15:01 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
2013-10-14 15:01 ` Phillip Susi [this message]
2013-10-18 9:36 ` Karel Zak
2013-10-18 11:57 ` Karel Zak
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