You can find the password from EC2 management console System Log.

1. Go to Amazon EC2 console at https://console.aws.amazon.com/ec2/.
2. Chose your Instance and Click Actions → Instance Settings → Get System log

Get System log

You can also SSH into your instance and find the login credential using the following command.

$ cat /home/ubuntu/credentials
////////////////////credentials info////////////////////
--- phpMyAdmin
----- Setting  : Success
--- MySQL
----- User     : root
----- Password : e1WFUFzvz1NaxiSo
////////////////////////////////////////////////////////

If you want to use a mysql user “debian-sys-maint”, please set up the password with the mysql root user.

mysql> ALTER USER 'debian-sys-maint'@'localhost' IDENTIFIED BY 'YOUR_PASSWORD';
mysql> flush privileges;