Hi,
on CentOS 7 Installation, when I try to update to MySQL 5.6 I got the error:
You cannot install MariaDB, because you do not have it set in options.conf file
Please advice,
There is no 5.6 version of MariaDB available, only 5.5 is available for DA installations for now. Next release of MariaDB is 10.x, which is not yet available in CB 2.0. MariaDB 5.6 is not released, and it won't be.
I would recommend mailing DirectAdmin support with a question about MariaDB 10.x support. At the moment, you could upgrade manually to 10.x, but not using CB 2.0.