[linux-lvm] recovering data from inside a partitioned lv

[linux-lvm] recovering data from inside a partitioned lv

[Anthony Clark]

Hi,

The following stupid mistake was made :(  A pv, vg and lv were  
created, and then the documentation was misread, and a partition was  
created inside the lv.  Said partition mounted fine, and allowed fs  
creation along with large amounts of data to be copied.  Partition was  
accessible via /dev/vg1/lv1p1.

Server has been rebooted, and now only /dev/vg1/lv1 is shown.  parted  
can open the lv and shows 1 partition inside, but doesn't understand  
ext3 volumes, so can't copy the partition to another disk.  tune2fs  
can't see /dev/vg1/lv1p1, or I'd use that to change the fs type to ext2.

Is there a way to undo the stupid mistake and get at the partition  
inside the logical volume?  That is to say, mount the partition, copy  
the data out and then create the filesystem correctly.  Is there a way  
to force /dev/vg1/lv1p1 to show up again?

Thanks in advance for helping :)

-a

Re: [linux-lvm] recovering data from inside a partitioned lv

[Christian Völker]

Hi,

> Server has been rebooted, and now only /dev/vg1/lv1 is shown.  parted
> can open the lv and shows 1 partition inside, but doesn't understand
> ext3 volumes, so can't copy the partition to another disk.  tune2fs
> can't see /dev/vg1/lv1p1, or I'd use that to change the fs type to ext2.
I think the partition entry under /dev is missing. After the initial
fdisk it was created.
So two ways to recover:
-Open fdisk on the lv. Do not do any changes, but leave and (w)rite. I'd
say the entries lv1p1 will be re-created then. Mount it, copy the data
and get rid of partition.
-Use loop device. This is much more complicated but will work, though:
losetup -o$[512*63] /dev/loop1 /dev/vg1/lv1
So it will create a loop device /dev/loop1 from lv1 with an offset of
512*63 (default blocksize and partitioning schema, may vary thought) .
And then simply mount the loop device with the "-o loop" option for
mount. Copy and get rid of partition.

Hope this helps, let us know if it does.
GReetings

Christian

Re: [linux-lvm] recovering data from inside a partitioned lv

[Bryn M. Reeves]

On Mon, 2009-06-22 at 13:23 -0400, Anthony Clark wrote:
> Hi,
> 
> The following stupid mistake was made :(  A pv, vg and lv were  
> created, and then the documentation was misread, and a partition was  
> created inside the lv.  Said partition mounted fine, and allowed fs  
> creation along with large amounts of data to be copied.  Partition was  
> accessible via /dev/vg1/lv1p1.
> 
> Server has been rebooted, and now only /dev/vg1/lv1 is shown.  parted  
> can open the lv and shows 1 partition inside, but doesn't understand  
> ext3 volumes, so can't copy the partition to another disk.  tune2fs  
> can't see /dev/vg1/lv1p1, or I'd use that to change the fs type to ext2.
> 
> Is there a way to undo the stupid mistake and get at the partition  
> inside the logical volume?  That is to say, mount the partition, copy  
> the data out and then create the filesystem correctly.  Is there a way  
> to force /dev/vg1/lv1p1 to show up again?

kpartx -a /dev/vg1/lv1

Will create maps for all the partitions defined inside the LV. See man
kpartx for the remaining options.

Cheers,
Bryn.

Re: [linux-lvm] recovering data from inside a partitioned lv

[Anthony Clark]

The loop device solution worked!

thank you Christian!
--
Anthony Clark - anthony@merit.edu
734 527 5744 - (aim)anthonyclark




On Jun 22, 2009, at 1:32 PM, Christian V�lker wrote:

> Hi,
>
>> Server has been rebooted, and now only /dev/vg1/lv1 is shown.  parted
>> can open the lv and shows 1 partition inside, but doesn't understand
>> ext3 volumes, so can't copy the partition to another disk.  tune2fs
>> can't see /dev/vg1/lv1p1, or I'd use that to change the fs type to  
>> ext2.
> I think the partition entry under /dev is missing. After the initial
> fdisk it was created.
> So two ways to recover:
> -Open fdisk on the lv. Do not do any changes, but leave and (w)rite.  
> I'd
> say the entries lv1p1 will be re-created then. Mount it, copy the data
> and get rid of partition.
> -Use loop device. This is much more complicated but will work, though:
> losetup -o$[512*63] /dev/loop1 /dev/vg1/lv1
> So it will create a loop device /dev/loop1 from lv1 with an offset of
> 512*63 (default blocksize and partitioning schema, may vary thought) .
> And then simply mount the loop device with the "-o loop" option for
> mount. Copy and get rid of partition.
>
> Hope this helps, let us know if it does.
> GReetings
>
> Christian
>
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> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/