Postgres 8.1.4 is not starting in RHEL 4

Hi
I installed 8.1.4 POSTGRESQL RPMS on my system. When I tried to run /etc/init.d/postgresql start I got this error.

[root(at)newdell init.d]# ./postgresql start
Initializing database: mkdir: cannot create directory `/var/lib/pgsql/data/pg_log': File exists
[FAILED]
Starting postgresql service: [FAILED]

Then i removed "pg_log" and given

[root(at)newdell data]# pg_ctl --log /tmp/pg.log start
pg_ctl: cannot be run as root
Please log in (using, e.g., "su") as the (unprivileged) user that will
own the server process.

Then i cahnged the user as postgres

[root(at)newdell data]# su postgres
bash-3.00$ pg_ctl --log /tmp/pg.log start
pg_ctl: no database directory specified and environment variable PGDATA unset
Try "pg_ctl --help" for more information.
bash-3.00$

Please help me

Thanks
Manish

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