Bug 69399

FreeBSD by default installs a very small /var partition for the user.  This small partition is used not only for mail, and 
logs (both of which can grow on occasion without warning), but the mysql-server port uses this location as the default 
location for all databases.  Additionally, the /var/tmp directory is used

Fix: 

The "fix" is something like:

mkdir /usr/var
cd /var
cp db /usr/var
ln -s /usr/var/db
cp tmp /usr/var
ln -s /usr/var/tmp

However, it's generally my opinion that at least a WARNING or something should be printed, as the default table types 
(especially InnoDB) tend to grow by fairly large increments.

Either an alternate location needs to be found for "big" semi-permanent files (/var is for mainly transient files -- it's not 
supposed to be a huge earth-shattering disaster if you lose /var), or that partition needs to be defaulted to something a lot 
bigger.
How-To-Repeat: 
cd /usr/ports/mysql40-server
make install

let logs and/or mail run for a while (especially easy if you've also installed apache from ports), as the apache logs are 
written to /var/log with no rotation.

Watch your tables corrupt themselves and mysql die with error 28 from the table handler.