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

[Roger Heflin <rogerheflin@gmail.com>]

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is the pv in the root device vg?  if not changing fstab to not mount the
missing  fs(es) should get it bootable.   I have a practice of putting
",nofail" on all non-root filesystems (ie defaults,nofail) since priority
#1 is getting the machine up and on the network after a reboot such that it
can be ssh'ed to and fixed as needed.

If it is not the root device then on the root device there should be
several prior archive copy in /etc/lvm/archive/<vgname>*, and maybe some
copies in /etc/lvm/backup.

In the vg backup file there will be a bunch of uuids, you want the specific
pv uuid and not the vg/lv uuids.  Each pv has a uuid and each lv has a uuid
and the vg has a uuid.

On Wed, Oct 20, 2021 at 8:39 AM Brian McCullough <bdmc@bdmcc-us.com> wrote:

> 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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>

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