rpm: change root directory

http://www.rpm.org/max-rpm-snapshot/rpm.8.html

--root DIRECTORY
Use the file system tree rooted at DIRECTORY for all operations. Note that this means the database within DIRECTORY will be used for dependency checks and any scriptlet(s) (e.g. %post if installing, or %prep if building, a package) will be run after a chroot(2) to DIRECTORY.

rpm -Uvh --root /myroot *.rpm



[Note]
You don't need to specify the dbpath if you've changed the root.
It will look into the new root to find the dababase.