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Re: [linux-lvm] Solution? found backup hexdump of partition's first MB



On Tue, May 29, 2001 at 08:20:30PM +0200, Jens Benecke wrote:
> On Tue, May 29, 2001 at 09:34:36AM +0200, Jens Benecke wrote:
> > On Tue, May 29, 2001 at 01:06:28AM +0200, Jens Benecke wrote:
> > > Hello,
> > > I upgraded to 2.2.4 (0.9.1-beta2) from 2.2.18 (LVM 0.9) and this seems to
> > > have killed one of my PVs. I tried the 0.9 utilities and updated to
> > > 0.9.1-beta7 when I noticed the problems. No change. Booting back to 2.2.18
> > > didn't help, the PV was gone there as well.
> > follow-up:
> > vgcfgrestore doesn't work, because LVM thinks my hdc1 is no PV. Here's the
> > output: (...)
> 
> I think I found a way: I have found a hex-dump backup of the first megabyte
> of the disk in - apparently - working order.
> 
> So: hdc1 was the broken PV, it's the only partition on hdc, and I have a
> file called hdc-first-MB-hexdump.
> 
> Does this help? ;)

Yes, in case it really contains the needed actual copy.


> 
> The question is, does this already contain file system data or is this
> still all LVM structure data?

If it is just a MB -> unlikely, because LVM typically reserves more
than that for the VGDA.

*But* to be really sure, run "pvdata -PP" on the hex dump and look
for pe_on_disk.base + pe_on_disk.size. This will give you the
actual end (in 512 byte units) of the metadata in the file and should
be used to dd it back to disk.


> I'm quite sure that the LVM structure didn't
> change since this file was created, only (of course) the data changed on
> the filesystem contained in the one (single) LV on data=(hdc1,hda1).

See above: you *need* to be sure. Hopefully the pvcreate/vgcfgrestore pair
           works for you.

> 
> 
> -- 
> Jens Benecke             /* Nobody will ever see this error message :-) */
>                             panic("Cannot initialize video hardware\n");
>                                   -- Linux 2.0.38,  arch/m68k/atari/atafb.c
> http://www.hitchhikers.de/ - Die kostenlose Mitfahrzentrale für ganz Europa
> _______________________________________________
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> read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen Sistina com                           +49 2626 141200
                                                       FAX 924446
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