At the initial start up of the server the following happens, given that the data directory of the server is empty:
To reveal it, use the following command:
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 -u root -p #Login to root user with some password
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass5!';