crie a senha do usuario postgres

passwd postgres

Logue no postgres

$ su postgres
$ psql -c "ALTER USER postgres WITH PASSWORD 'senha'" -d template1 

Edite o arquivo /etc/postgres/8.4/main/postgresql.conf e troque o conteudo

#listen_addresses = "localhost"

Para

#listen_addresses = "*"

Edite o arquivo /etc/postgres/8.4/main/pg_hba.conf e insira o conteudo

host    all         all         0.0.0.0/0             trust