Why can't I do this (setup question)

I've got PostgreSQL 7.1 installed from rpms on a RedHat 6.2 system.  I
want the data directory on a separate partition, so I shut down, tar the
whole directory into the other directory, mount it, and when I start up
postgresSQL it says it's up, but I can't connect to any databases using
psql.
psql: connectDBStart() -- connect() failed: Connection refused
        Is the postmaster running locally
        and accepting connections on Unix socket '/tmp/.s.PGSQL.5432'?
There is a postmaster running, but no socket in /tmp/

Here's the whole sequence of commands as root:
    mkdir data.new
    chown postgres.postgres data.new
    mount /dev/hdc6 data.new
    cd data.new
    (cd ../data; tar cvBf - .) | tar xvBpf -
    cd ..
    mv data data.old
    umount data.new
    mkdir data
    chown postgres.postgres data
    mount /dev/hdc6 data
    /etc/rc.d/init.d/postgresql start

Is there a way to make this work, or am I going to have to export and
import?

--
Paul Tomblin <ptomblin@xcski.com>, not speaking for anybody
Command, n.:
    Statement presented by a human and accepted by a computer in
such a manner as to make the human feel as if he is in control.