PAM implementation in PG 9.2.3

Hi All,

I am trying to implement PAM on my local machine.

Below are the details of my setup:

OS: RHEL 6
PG: 9.2.3

/etc/pam.d/postgresql (PAM file)

#%PAM-1.0
auth required pam_unix.so
account required pam_unix.so

$PGDATA/pg_hba.conf

# TYPE DATABASE USER ADDRESS METHOD

# "local" is for Unix domain socket connections only
local all all pam
pamservice=postgresql
# IPv4 local connections:
host all all 127.0.0.1/32 pam
pamservice=postgresql

Session 1 Session 2
-bash-4.1$ psql -U postgres
Password for user postgres:

-bash-4.1$ tail -f postgresql-2013-04-26_000000.log
2013-04-26 20:08:16.605 IST-13943-postgres-postgres-[local] LOG:
pam_authenticate failed: Conversation error
2013-04-26 20:08:16.606 IST-13943-postgres-postgres-[local] FATAL: PAM
authentication failed for user "postgres"
2013-04-26 20:08:16.606 IST-13943-postgres-postgres-[local] LOG: could not
send data to client: Broken pipe

In OS logs(/var/log/secure)

Apr 26 20:11:03 localhost res [local] authentication:
pam_unix(postgresql:auth): conversation failed

Apr 26 20:11:03 localhost res [local] authentication:
pam_unix(postgresql:auth): auth could not identify password for [postgres]

I have not entered password in session 1 which was waiting for my password
to enter, but logs are printed beforehand in both logs (OS/DB) as you see
in session 2.

When, I enter password in session 1 which was waiting for password, it will
immediately takes me into the database without any error.

Couple of question's in mind on this scenario:

1. Why database server logs shows lines beforehand as pam_authentication
failed even though I have not typed password ?
2. Though logs show as PAM authentication failed, still user's are allowed
into the database ?
3. What above log entries mean precisely ?
4. Was my PAM setup successful ?

Sorry for my too many questions, I just lost all of my endeavors to
understand the above scenario.

Any help will be highly appreciated.
Thanks in advance.

---
Regards,
Raghavendra