chicken feet revista

[Collins Richey]

How coincidental was it that we were discussing Waywar and chicken
feet on the list. I've just come through a situation yesterday where I
had to throw in chicken feet to get through a sticky wicket. The first
time in a long time that I was almost stumped.

It's sort of a long story, so be patient

Way back when (Nov 2005?) when I reorganized my disk drives to put
Kubuntu on the machine using an LVM setup, I inadvertently created a
situation where most of the space on my hda became unusable except for
the Ubuntu system. The drive is setup with /boot, / , and a large LVM
partition. I hadn't done the necessary RTFM to realize that it's
extremely difficult (certainly not impossible) to utilize LVM logical
volumes for booting. So I left that space idle and concentrated on hdb
for installing new distros, etc.

Now I have a free (legitimate) copy of VMware Workstation that I would
like to play with, so I decided it was time to clean out the cruft.
Using my trusty clone procedure, I began to work my way through moving
Kubunto to hdb. This procedure has always worked, and I was expecting
no surprises. Well, this time it almost worked and thus led to the
consultation of chicken feet, or actually a silver dagger, to slay the
Dracula-like beast. Here's the trivial procedure.

1. Carve out some partitions on HDB.
2. Clone the Kubuntu system from hda to hdb
3. Fix the new fstab
4. Fix the existing grub.conf on hda to boot the new Kubuntu on hdb
5. Reboot and check everything out
6. Install the new grub.conf on hdb
7. Reboot again and check everything out
8. Reformat hda to the new setup (no LVM)
9. Reboot and check everything out

Steps 1-8 worked flawlessly; no problem running the new clone, and the
MBR no longer pointed to the old (now gone) grub.conf on hda.

Step 9 led to a kernel panic looking for something on hda3 (now long
gone). The casting of chicken feet and bones commenced. Before
dragging out the Knoppix CD, I thought to boot the CentOS system (also
sitting on hdb), and this system continued to boot without error, so I
used it to debug the setup. Discovered no bugs in the grub.conf and no
bugs in the fstab Puzzling.

To make a long story short, when you eliminate an LVM setup on a disk,
it's as difficult to slay as Dracula. The host system retains some
info in /etc/lvm. Removed this data, but still kernel panic. I knew
from prior experience, that the disk needed to be cleaned up, so I
start with the usual (what I use at work to clean an LVM volume).

dd if=/dev/zero of=/dev/hda bs=512 count=1024

In the past, that has been enough, but not this time. Finally, after reaching

dd if=/dev/zero of=/dev/hda bs=512 count=132000

I was able to boot Kubuntu again.

The CentOS system had no problems, since I never used LVM at the time
it was installed.

I did some post-incantation RTFM, but found no useful information in
anly LVM howto on eliminating an LVM physical volume for use as a
regular volume. Apparently LVM leaves chicken tracks on the volume
well beyond the MBR area, and at least on Debian/Ubuntu systems the
LVM daemon does not allow recovery if an LVM physical volume has
become unusable.

So, keep those chicken feet or silver daggers handy.

-- 
Collins Richey
     If you fill your heart with regrets of yesterday and the worries
     of tomorrow, you have no today to be thankful for.