Update linux from 7.1 to 7.3 and couldn't get Psql7.0.3 back to work

%psql
psql: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/tmp/.s.PGSQL.5432"?

> It doesn't work The very first command gives me the error:
> ==========
> [root(at)(dot)(dot)(dot)]# /etc/rc.d/init.d/postgresql start
>
> 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-7.2/README.rpm-dist fo$
> more information.
> ===========
>
> It seems before that, I need to type the following as user postgres:
> =============
> The basic sequence is:
> (as user postgres):
> postgresql-dump -t /var/lib/pgsql/backup/db.bak -p /var/lib/pgsql/backup/old -d
> (you can abort the ASCII dump with 'Q', as it uses more) Then, (as user root):
> =================
>
> However, it seems there is no command postgresql-dump. I found a command
> called pg_dump in the /usr/lib/pgsql/backup directory. However when It
> substitute that for the other command, I get another error:
> =============
> bash-2.05a$ ./pg_dump -t /var/lib/pgsql/backup/db.bak -p
> /var/lib/pgsql/backup/old -d
> pg_dump: no database name specified
=============

Does any one has any clue? Any comments are greatly appriciated.

Thank you,

Xueying Ni