Bug#506582: grub2 will happily make unbootable systems with /boot on LVM

[Jim Studt]

Package: grub-pc
Version: 1.96+20080724-12

update-grub will happily work with kernels on an LVM partition even  
though the lvm module is not installed in the MBR.
The fix for this may well be to have...
	GRUB_PRELOAD_MODULES=lvm
... in /etc/default/grub and to do a grub-install, but that option is  
not documented anywhere and is only discoverable by reading the  
00_header script.

update-grub should detect if it is putting LVM or RAID mounted kernels  
and the corresponding modules are not in GRUB_PRELOAD_MODULES and  
print a warning lest it render the system unbootable.