pd_dump server mismatch error

Hi
I wanted to take a backup of my database.

pg_dump throws a server mismatch version error

# cd backups
# su - postgres
-bash-4.1$ pg_dump mydb > mydbfile
pg_dump: server version: 9.2.4; pg_dump version: 8.4.13
pg_dump: aborting because of server version mismatch

This is a fresh install of postgresql on a red hat linux server that did not have any previous database installed on it . I installed postgresql 9.2 from an rpm (pgdg-redhat92-9.2-7.noarch.rpm ) using yum install.

Why am I seeing this error?
How can I take a backup of my database? There are two tables that have 20,000+ rows in it, that I want to backup  and restore when needed.

thanks
thara.