Hi Venkatesh, login as the mysql's root from root system user on any controller without any password:

root@node-1:~# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 53528
Server version: 5.6.16-2~u14.04+mos2-log (Ubuntu), wsrep_25.5.rXXXX

Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

If you want to login as a user (OpenStack service), search the password in the configuration file, like /etc/keystone/keystone.conf:

root@node-1:~# cat /etc/keystone/keystone.conf | egrep ^connection
connection=mysql://keystone:BEz17Vos@192.168.0.2/keystone?read_timeout=60

root@node-1:~# mysql -u keystone -p
Enter password: [BEz17Vos]
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 53547
Server version: 5.6.16-2~u14.04+mos2-log (Ubuntu), wsrep_25.5.rXXXX

Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| keystone           |
| test               |
+--------------------+
3 rows in set (0.01 sec)

mysql>

You can find the password in

 /etc/mysql/conf.d/password.cnf

on any of the controllers

From https://docs.mirantis.com/openstack/f... it looks like it is set in a YAML config file.