On each disk in the volume group is a record of the changes that have
been made to the volume group. The last item in the record is the
current lvm meta-data. If you can retrieve that, it is the same as
having the backup file which would normally be found in
/etc/lvm/backup.
You could use hexdump, but I find it much simpler to use 'less -f
<device>'. You should see something like:
<crap>
principal {
...
}
<comments>
<crap>
principal {
...
}
<comments>
<crap>
You should be able to search for 'principal' (the name of your volume
group) to locate the first record. As I said, this "meta data area" of
the disk keeps a history of your volume group changes. That is, rather
than overwriting the record, it writes the new metadata format after
the last one (in a circular buffer fashion). You can use the 'seqno'
field to determine the newest one. Also, the metadata is written in
text to the disk, so it should be simple enough to read it and
determine if everything looks fine.
Once you've found the latest copy of the metadata, copy it - including
comments - to a file and use 'vgcfgrestore -t -f <file> <vgname>' to
test it. Once satisfied, perform the 'vgcfgrestore -f <file>
<vgname>'.
If all else fails, you can use dd to grab me the first chunk of the
disk, and I'll recreate the backup file for you. ('dd if=<one of the
good devs> of=<output file> bs=1M count=1; bzip2 <output file>; send
me <output file>.bz2')
brassow
On Oct 16, 2006, at 10:57 AM, Jerome wrote:
jbrassow wrote:
>does 'vgcfgrestore principal' work?
>
> brassow
>
Hi Jonathan,
i try to use this command, and i've received this error mesage:
/etc/lvm/backup/principal: stat failed: No such file or directory
Couldn't read volume group metadata.
Restore failed.
I mean that i've lost the /etc/lv/ directory lost. I've read some
information about how to construct the Metadata file with hexdump
command (cf :
https://www.redhat.com/archives/linux-lvm/2006-June/msg00049.html).
But i not sure how to do this yet.
Thank's a lot.
--
-- Jérôme
Il n'y a point de génie sans un grain de folie.
(Aristote)
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