I tried originally to upgrade Redhat 6.0 using files in the root partition to upgrade the same partition. It failed with a couldn't find RPM database error on the main screen. I rebooted and tried rpm --rebuild after upgrading to the Redhat 6.0 version of rpm. This did not help. Then I noticed on the other screen the error regarding a mount on /tmp/hdimage. So I copied all the files to another partition and got much further (till the problem I worked around in bugid 2506. Has anyone been able to use the same partition to upgrade itself? I only have a single root partition, no other partitions. Another note: bugid 2142 seems to mention this problem in the last comment but I think their other primary issue was resolved and so it was closed.
*** This bug has been marked as a duplicate of 2504 ***