​Login to the MAA Appliance using the g2 user or the Command Line option from the MAA local console.

Change to root context:
[email protected]:~# sudo -s

Show the password for mysql:
[email protected]:~# cat /root/mysql.root.pw

Start the mysql CLI:
[email protected]:~# mysql -u root -p

Show a table of all users:
mysql> select * from users;

The output will look like this:
+-----+---------------------+-------------------+--------------------------+----------+-------+
| uid | date_added          | label             | email                    | username | state |
+-----+---------------------+-------------------+--------------------------+----------+-------+
|   3 | 0000-00-00 00:00:00 | Administrator     | [email protected] | admin    |     0 |
|   4 | 2014-12-02 15:45:46 | SecurityAnalytics | [email protected]              | SA       |     0 |
+-----+---------------------+-------------------+--------------------------+----------+-------+
2 rows in set (0.00 sec)

Get the uid for the user you want to reset the password for. (In our example the uid 3 for user "admin").  Now, set the password back to the default value "admin" using this command: 
mysql> update ui_creds set pw = "$2a$12$ii50LBgnXMEDqUPE7GOZ1u9TQsPW8XxVaX8sQd0y41/vrF6s3zUDi" where uid = 3;

The response will be:
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

Exit mysql CLI:
mysql> quit;

Logout from the CLI /SSH session and try log into the UI with the password "admin".