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

[Roger Heflin]

replying to my last email.

do the pvcreate -uuid and then do a pvs/lvs/vgs and see if the vg/lv's look
like that are there.   if so do a vgchange -ay <vgname> and then test
mounting the fs.

And if with the fs either commented out and/or ,nofail the normal os boots
up work from there as you should have backup files.

On Wed, Oct 20, 2021 at 1:01 PM Roger Heflin <rogerheflin at gmail.com> wrote:

> 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 at 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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>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>
>>
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