## machine info

[root@VIRTCENT09 ~]# cat /etc/redhat-release
CentOS release 5.5 (Final)
[root@VIRTCENT09 ~]# uname -a
Linux VIRTCENT09 2.6.18-238.1.1.1.el5xen #1 SMP Mon Jan 24 11:02:21 NOVT 2011 x86_64 x86_64 x86_64 GNU/Linux


## restored old version of 8.1 data to postgresql-8.4.5 database



[root@VIRTCENT09 ~]# service postgresql restart
Stopping postgresql service:                               [FAILED]

An old version of the database format was found.
You need to upgrade the data format before using PostgreSQL.
See (Your System's documentation directory)/postgresql-8.4.5/README.rpm-dist for more information.