preupgrade stuck

I ran preupgrade on a box with some raid arrays and volume groups.  
Everything was working fine through the preupgrade portion but after I 
rebooted anaconda cannot find the root of the existing installation and 
the whole preupgrade is stalled (I opened a bug on this).  I can however 
boot into rescue mode and see the system and all the preupgrade packages 
are there.  How can I manually finish this preupgrade with just 'yum' 
from the rescue mode?

Regards,
Gerry