To install PostgreSql with RHEL is easy.
1. select PostgreSql(7.4.8) package shiped with RHEL to install.
2. The RHEL will create a user and a group named postgres.
3. The defalut path of postgre sql is /var/lib/pgsql, the database path is /var/ib/pgsql/data
4. modify postgresql.conf: tcpip_socket = true and port = 5432. modify pg_hba.conf to add following line: host all all 192.168.0.0/16 trust
5. to make postgresql bootable to run command: chkconfig --level 345 postgresql on. And check it with command that chkconfig --list postgresql
6. to start postgre sql with command: service postgresql start.
7. su - postgres
8. $ createdb test, $ createuser mutsu,
BTW, you have to change strategy of firewall on the RHEL.