How to create a user with password

Hi, all:

In the file of pg_hba.conf, I give the following parameter:

TYPE DATABASE IP_ADDRESS MASK AUTH_TYPE AUTH_ARGUMENT
Local all password
host all 127.122.122.0 255.255.255.0 password

Now look what I got:

$su postgres
bash$psql template1
$password

What is the password for user 'postgres' ? How can I create one for this
user?

bash$createuser dbadmin
Shall the new user be allowed to create database?(y/n) y
Shall the new user be allowed to create more new user? (y/n) y
password: 'dbadminpassword'
FATAL 1: password authentication failed for user "postgres"
Createuser: creation of user 'dbadmin' failed

If I change the config setting to

Local all trust

I can login to template1 database and create users and databases, but I
fail to give a password to a user. Look:

$su postgres
bash$createuser dbadmin with password 'dbpassword'

Now it seems the 'dbpasswod' became the created user.

Anybody knows how to create password for 'postgres' ? How to create a user
with password?

--------------------------------------------

Hong Jin
h1jin(at)ucsd(dot)edu