Description of problem:

2.6.18-1.2257.fc5xenU doesn't boot, presumably because of this message in the
boot log:

mount: could not find filesystem '/dev/root'


Version-Release number of selected component (if applicable):

Going to boot Fedora Core (2.6.18-1.2257.fc5xenU)
  kernel: /vmlinuz-2.6.18-1.2257.fc5xenU
  initrd: /initrd-2.6.18-1.2257.fc5xenU.img


How reproducible:

Always, on multiple domU machines.

Steps to Reproduce:
1. yum update to 2.6.18-1.2257.fc5xenU
2. boot domU
3. observe failure to create /dev/root
  
Actual results:

Some of the boot log:

Using config file "/etc/xen/cashnet".
Going to boot Fedora Core (2.6.18-1.2257.fc5xenU)
  kernel: /vmlinuz-2.6.18-1.2257.fc5xenU
  initrd: /initrd-2.6.18-1.2257.fc5xenU.img
Started domain cashnet
Bootdata ok (command line is  ro root=/dev/VolGroup00/LogVol00)
Linux version 2.6.18-1.2257.fc5xenU (brewbuilder.redhat.com)
(gcc version 4.1.1 20060525 (Red Hat 4.1.1-1)) #1 SMP Fri Dec 15 17:32:05 EST 2006
[snip]
device-mapper: ioctl: 4.7.0-ioctl (2006-06-24) initialised: dm-devel
Loading dm-mirror.ko module
Loading dm-zero.ko module
Loading dm-snapshot.ko module
Creating root device.
Mounting root filesystem.
mount: could not find filesystem '/dev/root'
Setting up other filesystems.
Setting up new root fs
setuproot: moving /dev failed: No such file or directory
no fstab.sys, mounting internal defaults
setuproot: error mounting /proc: No such file or directory
setuproot: error mounting /sys: No such file or directory
Switching to new root and running init.
unmounting old /dev
unmounting old /proc
unmounting old /sys
switchroot: mount failed: No such file or directory
Kernel panic - not syncing: Attempted to kill init!



Additional info:

2.6.18-1.2239.fc5xenU was the last in a long line of kernels to have worked
fine. Fortunately, I can roll back to 2.6.18-1.2239.fc5xenU without apparent
issue, but I haven't tried to upgrade anything in my dom0 yet.