During in-place upgrade, the old MySQL 5.1 RPM package is uninstalled and
the new MariaDB 5.5 RPM package is installed, but RPM does not take this
operations as an update. Note that the MySQL RPM renames /etc/my.cnf to
/etc/my.cnf.rpmsave on uninstall.

After installing MariaDB you should do the following to restore your old
configuration options:

  root> mv -vi /etc/my.cnf.rpmsave /etc/my.cnf

You can find more on: [link:https://access.redhat.com/articles/723833]

