f11 to f12 with preugrade doesn't find root device

[Gianluca Cecchi]

On Tue, Nov 17, 2009 at 6:19 PM, Gianluca Cecchi
<gianluca.cecchi at gmail.com> wrote:
> [snip]
>
> I get an error that previous root device could not be found, forced to exit
> installer....
> [snip]

Expanding initrd.img inside /boot/upgrade/ directory, I notice that
there is no reference to LVM....
Could it be the reason of not finding root device, that is on LVM?
Any way to rebuild this initrd.img including LVM?
Thanks,
Gianluca