undo LVM

[Dave Howorth]

Michel Racic wrote:
> Hi Luis
> 
> Yes I know how important backups are and I gave most of my urgent data
> backed up on various places but this 1TB disc is my main backup and My
> other disc crashed...
> 
> I'm too pussy to just try that out so I first have to get a new 1TB disc
> and dd (mirror) the disc so I can try this out on the mirror disc...
> 
> I don't think that vgreduce will work but i try as soon I have the
> mirror disc

I don't have a solution I'm afraid but here's my understanding:
(1) you've created a PV and VG but not an LV
(2) the result of (1) is that you have some LVM metadata written in
partition /dev/sdb1
(3) you need to replace that LVM metadata with whatever LUKS data was
there before
(4) AFAIK, LVM does not keep a copy of what was on the disk before it
writes its metadata (not unreasonable, neither do any other format
operations!)
(5) So there's no way that any LVM operation could help you. The best
effect that running any more LVM commands can have is nothing; the worst
case is further damage
(6) So AIUI, your only hope of recovering data is if LUKS keeps backups
of that area of the disk for some reason, or if it has some kind of
error recovery, or if the data layout is localised so you only lose a
few blocks (I know nothing at all about it)

i.e IMHO your question is really about how to recover lost LUKS data
blocks and nothing to do with LVM. Probably not what you want to hear,
sorry. :(

Dave