MariaDB
MariaDB is a MySQL fork that is developed and maintained by original MySQL developers organised under MariaDB Foundation. It is considered to be more open and is being distributed as default MySQL compatible database by majority of modern linux distributions.
MariaDB is a drop-in replacement for Oracle MySQL, you can use it with any stable supported Moodle version using standard mysqli drivers.
MariaDB driver
New feature
in Moodle 2.6!
Since Moodle 2.6 there is a dedicated driver for MariaDB. It is recommended to explicitly specify mariadb Moodle driver in config.php:
$CFG->dbtype = 'mariadb';
$CFG->dblibrary = 'native';
At the moment the driver is similar to MySQL but in the future the implementations may diverge significantly. Moodle MariaDB driver is not compatible with MyISAM database engine.
See MySQL for more information, the setup procedure is nearly identical.
FAQ
It fails during installation due to binlog_format configuration: In my.cnf file set binlog_format = ROW under [mysqld] and restart mysql service