Ext3 partition won't mount

Hi experts,

I have a server running Ubuntu 10.04 server, which is virtualizing another Ubuntu 10.04 server with qemu / kvm. For some reason somebody yesterday decided to press the power button on the physical server. The virtual server never came back up.

I opened up virt-manager and had a look at my virtual machine. It had just a blinking cursor. I had previously thought maybe it was fsck'ing but it didn't appear to be. I pressed a few buttons on the keyboard, trying to get some input, and all of a sudden it showed a message saying something like "skipping /backup" which is the partition that has all of my files on it. Ubuntu loaded but /dev/sdb was not mounted at /backup. I have not been able to mount it, it gave an error that I can't remember but it may have been about a superblock.

Anyway I'm analysing the partition with testdisk at the moment, but I don't really know what to do from here. Any suggestions? Am I screwed? I have some of the data backed up on an external drive, so that's a bit of a relief. The partition is just a .qcow2 file as well, so maybe there is something I can do from the physical server?

Cheers,
Michael
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mstrelanAsked:
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torimarConnect With a Mentor Commented:
I think you are already going into the right direction: TestDisk is the optimal first step. Try to use it to get the backup superblock locations and then feed this info to fsck:
http://www.cgsecurity.org/wiki/Advanced_Find_ext2_ext3_Backup_SuperBlock

If this won't help, you might also want to try and mount the Qemu image directly in your Ubuntu host system. I never did this myself, and I hope the info given here will suffice:
http://en.wikibooks.org/wiki/QEMU/Images#Mounting_an_image_on_the_host
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mstrelanAuthor Commented:
"To search for them, run TestDisk and in the Advanced menu, select the partition and choose Superblock."

No partition available
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torimarCommented:
How did you proceed? Did you boot the VM off a bootable CD?
I recommend Parted Magic for the purpose: www.partedmagic.com

Then follow this guide in order to check whether the partition table may be restored:
http://www.howtoforge.com/data_recovery_with_testdisk
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mstrelanAuthor Commented:
The actual data image is on a separate qcow2 image than the operating system, so assumably it is safe to do any fsck / testdisk etc type of stuff without a live disc because the data partition is not mounted.

I have tried to "analyse" in test disk but it did not find any partitions. I am going to try and mount the image directly in the host OS.
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mstrelanAuthor Commented:
UPDATE - Good news. On the host OS I was able to mount the disk image and access all my files! Yay!

qemu-nbd -c /dev/nbd0 data.qcow2
partprobe /dev/nbd0
mount /dev/nbd0p1 /mnt/data/
ls -l /mnt/data

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Now I just need to know how to get it to mount in the guest OS. I will try the e2fsck with alternate superblock, but I want to take a backup of the disk image first.
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torimarCommented:
That is really good news indeed.

For a backup, I assume it will suffice to copy the qcow2 file to a safe backup location, the continue to work on the original.
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torimarConnect With a Mentor Commented:
If the e2fsck method should not turn out to be viable, you may consider backing up the data files directly from the mounted image, then, inside the VM, format the non-functional disk and "refill" it from the backup - provided that VM has access to the external media used.
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mstrelanAuthor Commented:
Thanks torimar, the format / refill method will be my plan b if e2fsck doesn't work. I'm off to buy a bigger hard drive to back up the data. Will be back later to post my results and award points.
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mstrelanAuthor Commented:
Ok I wasn't able to fix the disk with testdisk or anything, so the best solution is to mount the image in the host os and scp all the files to a new partition. Thanks torimar for the help
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mstrelanAuthor Commented:
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