To reveal the default "root" password:
shell> sudo grep 'temporary password' /var/log/mysqld.log
Change the root password as soon as possible by logging in with the generated temporary password and set a custom password for the superuser account:
shell> mysql -uroot -p mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass5!';
Note: MySQL's validate_password plugin is installed by default. This will require that passwords contain at least one upper case letter, one lower case letter, one digit, and one special character, and that the total password length is at least 8 characters.