[linux-lvm] setting up LVM, lost everything with a typo
Craig Hagerman
craighagerman at gmail.com
Thu Oct 20 02:07:42 UTC 2005
Hi,
I recently got a new HD and thought it was about time I started using
LVM. Unfortunatly, I think I have ended up loosing all of my data due
to a typo. I would like to know if my data is lost forever. If not,
what can I do now to recover. Here is the whole story...
Craig
Originally it was set up with 2 HD like this:
hda - containing / /home /usr
sda - containing one big partition (/dev/sda2) for data storage (SATA drive)
I added a new SATA drive and used cfdisk to format it and make one big
partition (ext3). My plan was to create a LV on the new HD, copy
everything over from the old HD, then add that old HD to the new LV.
I followed the LVM HOWTO to create a vg etc:
% pvcreate /dev/sdb1
% vgcreate media_vg /dev/sdb1
% lvcreate -L 233G -n media_lv media_vg
% mke2fs -j /dev/media_vg/media_lv
% mount /dev/media_vg/media_lv /mnt/media
... and everything worked beautifully. I copied everything (188GB)
from sda2 onto the new LV successfully. So next was time to prep sda2
to be added to the LV.... this is where I screwed up.
% pvcreate /dev/sda2
Physical volume "/dev/sda2" successfully created
% vgextend media_vg /dev/sda2
Volume group "media_vg" successfully extended
... I was following some example on a web site, and typed in the wrong
device next. The web site had said to use fdisk to change the
partition type to 8e. This SHOULD have been sda, but I wrote sdb by
mistake:
$ fdisk /dev/sdb
Command (m for help): t
Selected partition 1
Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)
Command (m for help): p
Disk /dev/sdb: 251.0 GB, 251000193024 bytes
255 heads, 63 sectors/track, 30515 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 1 30515 245111706 8e Linux LVM
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device
or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
.... BUT.... I didn't notice the screw up. I wanted to see if the LV
would be automaticaly mounted on a reboot without having to add to
fstab or an init script (I have been told that this would happen on
Debian), so I rebooted.
Now neither disc can be seen or mounted. dmesg | tail shows this:
% dmesg | tail
EXT3-fs error (device sda2): ext3_check_descriptors: Block bitmap for
group 0 not in group (block 3258811534)!
EXT3-fs: group descriptors corrupted !
EXT3-fs error (device sda2): ext3_check_descriptors: Block bitmap for
group 0 not in group (block 3258811534)!
EXT3-fs: group descriptors corrupted !
VFS: Can't find ext3 filesystem on dev sdb.
... vgchange can't help out....
% vgchange -a y media_vg
Couldn't find device with uuid 'ZHl4Ak-mGS4-wFlF-4neF-G1Ed-GxWB-C4Smj6'.
Couldn't find all physical volumes for volume group media_vg.
Couldn't find device with uuid 'ZHl4Ak-mGS4-wFlF-4neF-G1Ed-GxWB-C4Smj6'.
Couldn't find all physical volumes for volume group media_vg.
Unable to find volume group "media_vg"
....vgdisplay can't see either disc (exact same story with lvdisplay)...
vgdisplay
Couldn't find device with uuid 'ZHl4Ak-mGS4-wFlF-4neF-G1Ed-GxWB-C4Smj6'.
Couldn't find all physical volumes for volume group media_vg.
Couldn't find device with uuid 'ZHl4Ak-mGS4-wFlF-4neF-G1Ed-GxWB-C4Smj6'.
Couldn't find all physical volumes for volume group media_vg.
Volume group "media_vg" doesn't exist
... and pvdisplay gives me...
% pvdisplay
Couldn't find device with uuid 'ZHl4Ak-mGS4-wFlF-4neF-G1Ed-GxWB-C4Smj6'.
--- Physical volume ---
PV Name /dev/sdb1
VG Name media_vg
PV Size 233.75 GB / not usable 0
Allocatable yes
PE Size (KByte) 4096
Total PE 59841
Free PE 193
Allocated PE 59648
PV UUID rlnV4y-B4eJ-Pyc0-RLJm-2Zbv-t04C-dxzU1A
--- Physical volume ---
PV Name unknown device
VG Name media_vg
PV Size 186.30 GB / not usable 0
Allocatable yes
PE Size (KByte) 4096
Total PE 47694
Free PE 47694
Allocated PE 0
PV UUID ZHl4Ak-mGS4-wFlF-4neF-G1Ed-GxWB-C4Smj6
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