NOTE:
Use following URL to open phpMyAdmin page:
http://<Public net IP>/phpMyAdmin
phpMyAdmin is an application for MySQL databases management. With it you can create, alter, drop, delete, import and export MySQL database tables. You can also run MySQL queries, optimize, repair and check tables, change collation.

Display default MySQL root password

cd /root/oneinstack #Must enter the directory execution under oneinstack
grep dbrootpwd options.conf #Display MySQL root password

As shown below:

Change MySQL root password

cd  /root/oneinstack  # Must enter the directory execution under oneinstack
./reset_db_root_password.sh

As shown below: