[linux-lvm] recover a pv from a disk with no partition table

["Brian J. Murrell" <brian@interlinx.bc.ca>]

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I need to recover a PV from a disk with no partition table.  I have a
disk which gives EIO errors trying to read from the first few blocks of,
so, no partition table.

Is there any way with LVM2, given that I have
the /etc/lvm/backup/<vgname> file that I can determine the offset into
the disk where the partition starts, so that I could do:

# losetup -o <offset> /dev/loop2 /dev/hde

to get the PV on /dev/loop2 and then be able to activate it with
vgchange and read it's LVs?

gpart tells me:

# losetup -o $((512*8)) /dev/loop2 /dev/hde
# gpart -vg /dev/loop2


dev(/dev/loop2) mss(512)

* Warning: strange partition table magic 0x0000.
...


Begin scan...
Possible partition(Linux ext2), size(19mb), offset(0mb)
   type: 131(0x83)(Linux ext2 filesystem)
   size: 19mb #s(39248) s(55-39302)
   chs:  (1023/255/0)-(1023/255/0)d (0/0/0)-(0/0/0)r
   hex:  00 FF C0 FF 83 FF C0 FF 37 00 00 00 50 99 00 00

Possible partition(Linux LVM physical volume), size(156315mb), offset(19mb)
   type: 142(0x8E)(Linux LVM physical volume)
   size: 156315mb #s(320133744) s(39304-320173047)
   chs:  (1023/255/0)-(1023/255/0)d (0/0/0)-(0/0/0)r
   hex:  00 FF C0 FF 8E FF C0 FF 88 99 00 00 70 DA 14 13

Which looks right, but:

# losetup -o $((512*39304)) /dev/loop3 /dev/hde
# vgscan

Yields no new volume groups.  Neither does the above with 512*39303 or
512*39305 so it doesn't seem to be an off-by-one.  Nor does any of
512*(39303-8), 512*(39304-8), 512*(39305-8) to account for the fact that
loop2 (which the gpart was done on originally) is 8 blocks into /dev/hde
already.

Am I missing something?

Thanx,
b.

-- 
My other computer is your Microsoft Windows server.

Brian J. Murrell

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