Recursive destructive chgrp

[Szabó András <szundi@gmail.com>]

Hi!

I have a machine, that has run a script that set the group id of all files on the whole / partition to a given group.
How can I restore the original state? Is there a procedure of
reinstalling all the packages including the /dev structure and all
others? The rest could be set back in a few hours :)

Thanks
András