Re: [linux-lvm] Recovering "broken" disk ( 17th )

From: Roger Heflin <rogerheflin@gmail.com>
To: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] Recovering "broken" disk ( 17th )
Date: Mon, 18 Oct 2021 09:49:44 -0500	[thread overview]
Message-ID: <CAAMCDedrphwa+RRr1PHLD0SXi8fEDM87zV82302T=twRa5qBZA@mail.gmail.com> (raw)
In-Reply-To: <20211018021719.GA16936@bdmcc-us.com>

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You will need a lvm backup file for the pvcreate --uuid I believe (there
may be some option to get around needing the backup file).

That will put the header back on if you either have an lvm backup and/or
archive file, you might also need a vgcfgrestore afterwards depending on if
anything else is missing.

I have never done it, but it looks possible to make a lvm backup file by
reading it directly off the disk with dd, so that you will have a file that
pvcreate is ok with, that is if there is no way to force it without a
backup file.

But, this should get the pv back showing up with whatever sectors that you
successfully recovered.

On Sun, Oct 17, 2021 at 10:02 PM Brian McCullough <bdmc@bdmcc-us.com> wrote:

>
> Folks,
>
> I have had a disk go bad on me, causing me to lose one PV.
>
>
> I seem to have retrieved the partition using ddrescue, but it also seems
> to be missing some label information, because pvscan doesn't see it.
>
> Using hexdump, I see the string " LVM2 " at 0x1004, but nothing before
> that.  The whole phrase is:
>
> 0x01000  16 d6 8e db 20 4c 56 4d  32 20 78 5b 35 41 25 72
>
>
> I find what appears to be an LVM2 configuration section at 0x1200, and
> so I was able to read the UUID that this PV should have.
>
>
> On another machine, I dumped a PV partition, and find "LABLEONE" at
> 0x200, with the same " LVM2 " at 0x01000.
>
> I was concerned that my dump was offset, but the comparison to the
> "good" one suggests that that isn't the problem, but just the missing
> "LABLEONE" and related information at 0x0200.
>
> If I do a "pvcreate --uuid xxxx" would this fix that recovered partition
> so that pvscan and friends can work properly, and I can finally boot
> that machine?
>
>
> Thank you,
> Brian
>
>
> _______________________________________________
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> linux-lvm@redhat.com
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> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
>

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