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From: Brian McCullough <bdmc@bdmcc-us.com>
To: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] Recovering "broken" disk ( 17th )
Date: Wed, 20 Oct 2021 09:38:28 -0400	[thread overview]
Message-ID: <20211020133828.GE9096@bdmcc-us.com> (raw)
In-Reply-To: <CAAMCDeeTwESRvs5jPNuTXn-q7Fse1xqAc+yd-0swjc7NrAyqAw@mail.gmail.com>

On Tue, Oct 19, 2021 at 05:06:37AM -0500, Roger Heflin wrote:
> I would edit the vgconfig you dd'ed with an editor and make sure it looks
> reasonable for what you think you had.

It turns out, comparing the information that I pulled off of the drive
with what I find in /etc/lvm/backup, that the first part of the vgconfig
information is missing.  As I said in one of my messages, the
information that I retrieved from the disk starts at 0x1200.  I don't
know whether that is correct or not.  It does not appear to be a proper
"backup" file, which I think it should be.

I rebooted ( partially ) the machine and copied the vgconfig backup file
from that, but am somewhat concerned, because I don't seem to be able to
match the UUIDs.  The one that I seem to see in the vgconfig data that I
pulled off of the drive vs what I got out of /etc/lvm/backup.  Maybe I
am just mis-reading it.  I will continue my research for a bit.




> When you do the pvcreate --uuid it won't use anything except the uuid info
> so the rest may not need to be exactly right, if you have to do a
> vgcfgrestore to get it to read the rest of the info will be used.

Oh, thank you.   I did see that things got somewhat different on the
target drive when I did "pvcreate --uuid --restorefile."  I got paranoid
when I saw that, and re-copied the ddrestore file back to the target
drive before I did anything else.   Should I do "pvcreate --uuid
--norestorefile," instead?  Then, once it is back in the machine, do the
pvscan and vgcfgrestore, and expect good things?



> I have seen some weird disk controller failures that appeared to zero out
> the first bit of the disk (enough to get the partition table, grub, and the
> pv header depending on where the first partition starts).

I APPEAR to have a partition table, containing an NTFS partition, an LVM
partiton ( the one that I am concentrating on ) and a Linux partion.  I
would have thought that it was all LVM, but my memory could easily be
wrong.



> You will need to reinstall grub if this was the bootable disk, since there
> were 384 bytes of grub in the sector with the partition table that you know
> are missing.

Fortunately, this is all data, nothing to do with the boot sequence,
except that the machine will not boot with the missing PV.



Thank you,
Brian

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  reply	other threads:[~2021-10-20 13:39 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-18  2:17 Brian McCullough
2021-10-18 14:49 ` Roger Heflin
2021-10-18 19:45   ` Brian McCullough
2021-10-19 10:06     ` Roger Heflin
2021-10-20 13:38       ` Brian McCullough [this message]
2021-10-20 18:01         ` Roger Heflin
2021-10-20 18:04           ` Roger Heflin
2021-10-21  6:13             ` Brian McCullough

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