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[linux-lvm] Re: vgscan - volume group not found, panic!

On Fri, May 25, 2001 at 12:38:04AM +0200, Gerben Meijer wrote:
> Dear LVM users and developers,
> I am experiencing problems with LVM. I am running Debian GNU/Linux 2.2 with
> a 2.4.3-ac11 kernel, and LVM utils v0.9 (i use the packages from bunk at
> http://people.debian.org/~bunk/debian/dists/potato/main/binary-i386/). I had

(note to developers: i am starting to believe taht bumping IOP in b6 was not such
a bad idea, if that helps us getting rid of broken tools.
mebbe we should bump IOP in vanilla kernel....)

> Then I decided to try to upgrade to the latest LVM version, both in the
> kernel and the userspace utilities. So i patched my 2.4.3 kernel with the
> latest LVM patches (0.9.1beta7). I got an error while compiling my kernel
> though, get_hardblocksize wasn't defined anywhere. So i went back digging on

just replace get_hardblock_size with get_hardsect_size in drivers/md/lvm.c
or get latest version from cvs

> google and found one patch that fixed that for me:
> http://www.stacken.kth.se/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.4a
> a2.bz2.

i dunno which LVM version does andrea use in his patches

> So finally i had a working kernel with the latest LVM drivers, and i had the
> latest LVM userspace utils, and i had my hopes up. Unfortunately, vgscan
> still didn't see anything, and vgcfgrestore gave me an error
> (vg_check_consistency_with_pv_and_lv).
> Next, I tried using 2.4.4-ac9 with the original 0.9 userspace utilities.
> Still nothing.

in case you did not guess it from my note above original 0.9 userspace utils are bad
for your health

> I'm out of options here, and I am hoping that you can help me rescue my
> data. If you have any idea what I could try to fix this, please let me know.
> Debugged output i created:
sigh this debug output is very hard to read, anyway at the end you see
<55555> pv_read_uuidlist -- LEAVING with ret: 2
this means it only found the uiid for 2 PV (not 3)
they are u9.... and M4.... (sda1 and hda2)
cross checking with pvdata output shows you have a known problem

i'll attach a mail from Andreas Dilger with a solution for this.

good luck!

Luca Berra -- bluca comedia it
        Communication Media & Services S.r.l.
 / \
--- Begin Message ---
Diederick van Dijk writes:
> I've a LVM of 8 physical volumes that I've created with LVM 0.9.1 beta 2.
> I've the know problem that vgscan reports that it can't find my VG.
> So I upgraded to LVM 0.9.1 beta 6 (tools and kernel) and runned on each
> physical disk a vgcfgrestore. Unfortunately I didn't solve the problem.
> Attached is the output of the commands vgdisplay -v and a pvdata -U for each 
> physical disk. Debug logs a very huge so I won't attach them.

OK, I have figured out why vgcfgrestore doesn't work properly with broken
UUIDs.  It is because vgcfgrestore only restores the backup VGDA data to
each disk separately.  This means it is not possible to have consistent
UUIDs generated for all PVs in a VG when vgcfgrestore is run.

You can try the following (experimental) procedure to fix the UUIDs:

Check each PV with "pvdata -PP /dev/hdX" to ensure it has a valid
UUID assigned.  Also get the PV numbers (starting with 1) for each of
the PVs.  Finally, check the pv_uuidlist_on_disk.base for each PV.
It will normally be 6144, but it does not have to be.

for each PV (in PV# order)
    dd if=/dev/hdX bs=1 skip=44 count=128 >> /tmp/uuids

This should create a file /tmp/uuids which has all of the PV UUIDs in it.
Make sure there are as many UUIDs in the file ("od -a /tmp/uuids" is good)
as you have PVs (8 in your case).

Now, we want to write the UUID list back to the PVs so vgscan is happy:

for each PV (in any order)
    dd if=/tmp/uuids of=/dev/hdX bs=1 seek=<pv_uuidlist_on_disk.base for hdX>

    dd if=/tmp/uuids of=/dev/hda2 bs=1 seek=6144

Now vgscan should be able to detect all of the disks and work properly.

Cheers, Andreas
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert
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