--master-user-password

• aws rds modify-db-instance --master-user-password
• aws rds create-db-instance --master-user-password

Related

• --master-username
• root

See also

• aws rds create-db-instance
• AWS RDS: AWS::RDS, aws rds [ create-db-instance | create-db-instance-read-replica | describe-db-instances | modify-db-instance | modify-db-cluster | create-db-subnet-group | delete-db-instance | create-db-snapshot | aws rds create-db-parameter-group ], AllocatedStorage, FreeStorageSpace