FreeBSD?does not automatically include a default?my.cnf?for?MySQL. Instead, a set of sample configuration files can be found under?/usr/local/share/mysql. These configuration files include?my-small.cnf,?my-medium.cnf,?my-large.cnf,?my-innodb-heavy-4G, and?my-huge.cnf. The appropriate file can be copied and used as a template configuration by performing the following actions:

cd /usr/local/share/mysql/
cp /usr/local/share/mysql/mysql-large.cnf /usr/local/etc/my.cnf
/usr/local/etc/rc.d/mysql-server restart

http://www.barik.net/archive/2008/05/26/114616/