Re: Access Old Home Directory - USB enclosure - LVM

Robert L Cochran wrote:

Jim Cornette wrote:

Robert L Cochran wrote:

Jim Cornette wrote:

Robert L Cochran wrote:

https://www.redhat.com/archives/fedora-list/2005-April/msg01943.html

From an earlier posting someone suggested to run the following commands to activate and later deactivate LVM volumes in rescue mode. I used these commands on an external USB drive to get at data from a previous installation and it worked. You might be able to get at your data in this way.

Jim


lvm lvscan
lvm vgchange -ay

I'd like to follow up on this. Here is what I did.

1. Booted machine in rescue mode, using my install DVD, with the external USB drive containing my other FC4 system plugged in.

I booted into my regular installation. I then ran 'lvm vgchange -ay' to activate the lvm volumes. I think that I did a pvscan to get the information about the available lvms.

2. Executed 'chroot /mnt/sysimage'.

This would simple activate your system without all of the normally loaded tools. This is good information for if you needed to mount your system in rescue mode in the future.

3. Ran 'lvm lvscan' as suggested. I got this output.

ACTIVE 'dev/VolGroup00/LogVol00' [370.53 GB] inherit
ACTIVE 'dev/VolGroup00/LogVol01' [1.94 GB] inherit

The above logical volumes seem to reference my 400 Gb hard drive in my new, upgraded system, not the 60 Gb drive which is connected by USB.

The 'vgchange -ay' command might be needed to add additional volumes that might have labelling which conflict with your newly mounted system.

lvscan might then recognize the volumes on the USB enclosure drive.

I then unplugged the USB cable for my 60 Gb drive and re-plugged it in. Executing 'lvm lvscan' then got me this output:

/dev/sdb1: open failed: no such device or address
/dev/sdb2: open failed: no such device or address
/dev/sdb3: open failed: no such device or address

/dev/sdb3 seems to be where your LVM is located.

ACTIVE 'dev/VolGroup00/LogVol00' [370.53 GB] inherit
ACTIVE 'dev/VolGroup00/LogVol01' [1.94 GB] inherit

Question: should I have manually mounted the partitions before issuing 'lvm lvscan'?

I am not sure if it is possible to mount a partition with lvm volumes on it. I would imagine that filesystem is not correct would result from attempting to mount /dev/sdb3.

************ (Removed rescue CD, boot back into Fedora Core 4 on new system) ************

I then read the entire LVM how-to for lvm2 on tldp.org. It doesn't offer practical advice for this situation -- rescuing data from an older lvm-based system.

Go figure, real life situations never seem to match intended use for systm designs.

I also read 'man lvm', with no better results.

I then checked Bugzilla. There are 124 (or is it 125?) bugs listed for LVM.

It is looking more and more like I'll need to take out my 400 Gb drive and substitute my 60 Gb drive/120 Gb drive, and boot into that system, all to recover a little more data. Perhaps I need to quit using LVM.

Not adding a detour to those that use LVM, but adding a "me too" to LVM usage. If you do have to take drastic measures and re-install the drive from the USB enclosure, add this fact to the list. I did get this to work for once and recovered data from the drive contained in the USB enclosure. I really don't recall the exact steps that I took to get at the drive. It mounted and I did retrieve the information from the drive.

Since you have LVMs on your new system also, probably the dev/VolGroup00/LogVol00 identity is the same for both disks. It might have worked for me because I had no new LVMs on the running system.

Give system-config-lvm a try and see if you can manipulate the USB drive on a running system. If not, you may be out of luck and need to swap the drive out and backup your desired information onto a DVD or other media.

I'm sure the information is on the LVM, but in what format, I don't know. (dev/VolGroup00/LogVol00 also or different)

Jim

Thanks

Bob Cochran

To continue the saga, I took my machine apart to investigate this and spent part of the evening swapping drives in and out. I really feel like I'm paying big for not understanding how LVM works -- and remaining in blissful ignorance for a couple of years, too.

My Asrock motherboard has an option for booting from USB, so I tried to boot my 60 Gb drive from USB (in order to avoid taking it out of the external enclosure.) This gave me a black screen with these letters:

LI

I have some memory that this is the word LINUX and how many letters of the word are spelled out on the screen indicate something about the nature of the boot problem. No doubt, to boot from USB, I need code that can speak USB-ese. So much for this option.

I took the drive out of the enclosure, and connected it to the motherboard's SATA connector (There are 3, and I used the one numbered SATA1.) I When I turned on the power, the exprected GRUB screen came up, and when I booted the 1653 kernel, a kernel panic resulted. I got this message:

Unable to find volume group  "VolGroup00"

So now I'm confused. It looks to me like Grub is installed on my 60 Gb drive (that's why I got the nice splash screen) but the actual volume group is defined on my 120 Gb drive? This 120 Gb physical drive is (or was) really an older system. I thought I had one system installed on each of two different drives. I thought the 60 Gb drive was devoted to Fedora Core 4 and the 120 Gb drive was an older release, Fedora Core 3.

Bob Cochran

Bob Cochran