title: mysqld service won't start
body: <p>After Fedora 28 decided to upgrade mysql-community packages to 8.0 (latest) ,I realized my application was failing and had to downgrade to mysql 5.27.2</p>
  
  <p>Of course my db files (.idb) were the same (altered by mysql 8.0).
  When starting mysql 5.27 service, it fails. I have read the log file /var/log/mysqld.log and found this:</p>
  
  <blockquote>
    <p>InnoDB: Table flags are 0 in the data dictionary but the flags in
    file ./ibdata1 are 0x4000!</p>
  </blockquote>