Odoo system has three different passwords:
1) Paremeter admin_passwd in openerp-server.conf
This password allows you to manage databases, when you browse address
localhost: 8069 / web / database / manager
In this case, to set new: Remove the semicolon at the line start, set your password and restart odoo.
2) Paremeter db_password in openerp-server.conf
This is the password of role with name odoo in postgresql (parameter db_user = odoo in openerp-server.conf)
In this case, to set new, see https://www.postgresql.org/docs/9.0/static/sql-alterrole.html
In your case this password probably is empty (db_password = False)
3) Main Odoo user password, user with login = admin (or with your email).
In this case, to set new, replace the password and hash in the database with the new one by running this SQL query:
UPDATE res_users SET password = "NEW_PASSWORD",password_crypt = NULL WHERE id=1;
To retrieve login:
SELECT login, password FROM res_users WHERE id=1;
IMPORTANT!!! After update res_users (after setting NEW_PASSWORD) you login to Odoo and set new password again (If you need crypted password in database)