CentOS - Apr 2011 - Kickstart and lvm

I've written some %pre code to grab a few files off a logical volume, if it
exits, before the disk gets formatted, but can't get get it to work
correctly.

Essentially:

%pre
...
lvm vgscan
lvm vgchange -a y
...
if [ -d /dev/vol0 ]; then
  # do stuff
fi
lvm vgremove -f vol0

The problem is that /dev/vol0 does not exist after lvm vgchange. I added a
few debug statements (lvm pvdisplay, lvm vgdisplay, lvm lvdisplay, ls -l /dev)
that confirm the existance of all logical volumes, but there's no sign of
the volume group under /dev. What am I missing?

It appears adding
> %pre
> ...
> lvm vgscan
 lvm lvm vgimport vol0
> lvm vgchange -a y
> ...
> if [ -d /dev/vol0 ]; then
>   # do stuff
> fi
> lvm vgremove -f vol0
 
 makes the volume group appear in /dev. That was definitely not need on
 other hw.