Recovering data from a hard drive with LVM a partition

ShadyCraig · 01-18-2010, 06:19 AM

Hello all,

I have an external USB hard drive that I need to recover some data from, but I see from fdisk -l that the partition uses LVM:

Code:

[root@localhost ~]# fdisk -l /dev/sdd

Disk /dev/sdd: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1   *           1       19457   156288321   8e  Linux LVM
[root@localhost ~]#

I've followed various lvm tutorials all of which describe setting up lvm from fresh on empty disks. Unfortunately non mention how to 'install' new a drive that was previously set up with lvm.

I have had a go anyway and may have now lost my data. Here's what I've ended up with (the partition in question is sdd1):

Code:

[root@localhost ~]# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdd1
  VG Name               vg02
  PV Size               149.05 GB / not usable 1.31 MB
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              38156
  Free PE               12
  Allocated PE          38144
  PV UUID               HmVjPK-gHmG-LJqF-jy1c-fQwK-M1KL-t0MlKs

  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               VolGroup00
  PV Size               7.90 GB / not usable 23.41 MB
  Allocatable           yes (but full)
  PE Size (KByte)       32768
  Total PE              252
  Free PE               0
  Allocated PE          252
  PV UUID               400PwS-P1j1-uQP0-2pNq-rqsL-DiNW-VYbM5j

Code:

[root@localhost ~]# vgdisplay
  --- Volume group ---
  VG Name               vg02
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               149.05 GB
  PE Size               4.00 MB
  Total PE              38156
  Alloc PE / Size       38144 / 149.00 GB
  Free  PE / Size       12 / 48.00 MB
  VG UUID               TSEAlK-3HlT-utMW-0JEm-n45l-Hgmb-Vu4u1E

  --- Volume group ---
  VG Name               VolGroup00
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               7.88 GB
  PE Size               32.00 MB
  Total PE              252
  Alloc PE / Size       252 / 7.88 GB
  Free  PE / Size       0 / 0
  VG UUID               BGOVZ1-5U0e-3ATo-XQLG-82l1-uuc8-hhaizP

Code:

[root@localhost ~]# lvdisplay
  --- Logical volume ---
  LV Name                /dev/vg02/lv02
  VG Name                vg02
  LV UUID                c2Ztsz-7yak-N5W0-aYs1-xXZd-lXQO-kC3VOs
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                149.00 GB
  Current LE             38144
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:2

  --- Logical volume ---
  LV Name                /dev/VolGroup00/LogVol00
  VG Name                VolGroup00
  LV UUID                gbFYmV-F8uI-81R5-mYSg-p8KW-HNgo-V0R4hg
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                7.38 GB
  Current LE             236
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

  --- Logical volume ---
  LV Name                /dev/VolGroup00/LogVol01
  VG Name                VolGroup00
  LV UUID                cCVgp7-5bXf-wfng-nyQO-e77D-aHgd-CBsI0B
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                512.00 MB
  Current LE             16
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:1

Code:

[root@localhost ~]# mkdir /media/sdd1/
[root@localhost ~]# mount /dev/vg02/lv02 /media/sdd1/
mount: you must specify the filesystem type
[root@localhost ~]# mount -t ext3 /dev/vg02/lv02 /media/sdd1/
mount: wrong fs type, bad option, bad superblock on /dev/vg02/lv02,
       missing codepage or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

I've tried mounting with other fstypes, but all give the same error.

Can anyone help me recover my data please?

Thanks,
Craig

jschiwal · 01-18-2010, 07:16 AM

Use "/sbin/vgmknodes" to create the /dev/dm-* nodes for the logical partition on the LVM volume. Then mount those nodes.

ShadyCraig · 01-18-2010, 10:36 AM

Hi jschiwal,

Thanks for your reply, unfortunately it didn't help on this occasion.

At first vgmknodes didn't seem to do anything, especially as nothing appears in /dev/dm-*, not even for the working LVM drives.

So I ran 'vgmknodes -v -v', part of the output is here:

Code:

      /dev/sdd1: lvm2 label detected
      Locking /var/lock/lvm/V_vg02 RB
      /dev/sdd1: lvm2 label detected
      /dev/sdd1: lvm2 label detected
      Removing /dev/vg02/lv02
      Linking /dev/vg02/lv02 -> /dev/mapper/vg02-lv02
      Unlocking /var/lock/lvm/V_vg02

So I guessed that my system uses /dev/mapper rather than /dev/dm-.

Next I tried 'mount /dev/mapper/vg02-lv02 /media/sdd1'', this failed as before, the same goes for using -t:

Code:

[root@localhost ~]# mount /dev/mapper/vg02-lv02 /media/sdd1/
mount: you must specify the filesystem type
[root@localhost ~]# mount -t ext3 /dev/mapper/vg02-lv02 /media/sdd1/
mount: wrong fs type, bad option, bad superblock on /dev/mapper/vg02-lv02,
       missing codepage or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

Thanks again,
Craig

r0b0 · 01-19-2010, 03:54 AM

You are mounting the correct device (either path should work). I think the problem is either with broken filesystem (try fsck) or another filesystem type (try using mount without the -t option).

jschiwal · 01-19-2010, 06:47 AM

A quick check on a partition is to run "sudo file -s /dev/<device>". It will tell you what filesystem is on it. Then you can run fsck.<filesystem> to check the filesystem for errors.

Sometimes there is a filesystem in /dev/mapper/ and another such as /dev/dm-0.

Also look at "ls -l /dev/disk/by-uuid/" and follow the links. Using UUID=<UUID #> in /etc/fstab is preferable for external drives.

ShadyCraig · 01-19-2010, 07:47 AM

Quote:

Originally Posted by r0b0

You are mounting the correct device (either path should work). I think the problem is either with broken filesystem (try fsck) or another filesystem type (try using mount without the -t option).

Thanks robo, I tried mounting without the -t, but when that failed I tried using explicit types.

Quote:

Originally Posted by jschiwal

A quick check on a partition is to run "sudo file -s /dev/<device>". It will tell you what filesystem is on it. Then you can run fsck.<filesystem> to check the filesystem for errors.

Sometimes there is a filesystem in /dev/mapper/ and another such as /dev/dm-0.

Also look at "ls -l /dev/disk/by-uuid/" and follow the links. Using UUID=<UUID #> in /etc/fstab is preferable for external drives.

It never occurred to me to use 'file' in that way, that's really handy!

Unfortunately I think I have a stuffed file system :-( as 'file' doesn't come back with anything useful, and I think I've done everything correctly.

I'll have to read up on the UUID stuff as it didn't make sense on my system, the UUIDs in there weren't used by anything listed by pv/vg/lvdisplay. Thanks for the pointer though.

Thanks for your help but I'll give up on this now,
Craig

jschiwal · 01-21-2010, 02:03 AM

Be sure you use "file -s" on the logical volume. Using it on a Physical volume or volume group won't give you a filesystem.

If the logical volumes were used to create a raid array, then you may not have a filesystem on the logical volume.