you need to edit the pg_hba.conf file (it has lots of examples and directions inside it) to allow your servers to connect to postgresql, and you need postgresql to be started with a -i switch.
I found tha ton redhat 6.2, it was better remove the postgres startup script and replace it with pg_ctl renamed to postgres.
then edit the postmaster.opts.default file to include the -i switch and all should be well.