I had attempted to upgrade my Ubuntu/Dapper server (it had many things on it, including Web, SSH, XWindows, and the beginnings of Mail) from Dapper (5.x) to Feisty (7.x, currently in beta). I do the usual upgrade items for any Debian based distribution, change my sources, update the source list and do a dist-upgrade.
From Dapper to Edgy (6.x). Worked with little fuss. No problems.
From Edgy to Feisty... well... to make it short, I lost contact with my Logical Volume Manager definitions.
When I rebooted the machine at 0300 this morning after finishing the update (with much complaining) I rebooted, figuring the complaining to be nothing more than warnings about localization and such.
Well, the machine started.. but not much else. I couldn't load the root file system after boot, so it just sat there. Bummer.
I dd'ed myself a copy of the hard drive, to ensure that I had a recoverable copy of my data in the event that I hosed anything too much. Then I started digging, thinking that I had formatted the file system in ext2. Well, I did, technically. INSIDE THE LVM PARTITION!!! BAH!!! I'M SUCH A USER!!! It took my brain a few minutes to think about "hey, let's use fdisk and figure out what that partition is exactly!".
Actually, LVM isn't that bad of a thing. It's just a bit of overkill for a 20GB drive that's in no danger of filling up.
Anyway, I consult our benevolent almighty data overlords Google for info recovering LVM partitions, and lo, I find the this. Section 7 to be exact. I'm currently copying the data from the recovered partitions to an external USB drive as I type this. I should be able to format the drive and start over tomorrow, with all of my data. Thanks Richard!