For a long time I've known that the default installation of MySQL leaves behind a test database and several extraneous user permissions.  I've always tried to remember to remove these using phpMyAdmin, but sometimes it's easy to forget.  As a result of the recent HeartBleed incident, I've been taking a closer look at security.  One of the things I discovered is that MySQL has included a script, mysql_secure_installation, which removes the test database and secures the server for production.

# mysql_secure_installation

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MySQL
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!

In order to log into MySQL to secure it, we'll need the current
password for the root user.  If you've just installed MySQL, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.

Enter current password for root (enter for none):
OK, successfully used password, moving on...

Setting the root password ensures that nobody can log into the MySQL
root user without the proper authorisation.

You already have a root password set, so you can safely answer 'n'.

Change the root password? [Y/n] n
 ... skipping.

By default, a MySQL installation has an anonymous user, allowing anyone
to log into MySQL without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n] y
 ... Success!

Normally, root should only be allowed to connect from 'localhost'.  This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n] y
 ... Success!

By default, MySQL comes with a database named 'test' that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.

Remove test database and access to it? [Y/n] y
 - Dropping test database...
ERROR 1008 (HY000) at line 1: Can't drop database 'test'; database doesn't exist
 ... Failed!  Not critical, keep moving...
 - Removing privileges on test database...
 ... Success!

Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.

Reload privilege tables now? [Y/n] y
 ... Success!

Cleaning up...


All done!  If you've completed all of the above steps, your MySQL
installation should now be secure.

Thanks for using MySQL!

I recommend that all administrators run this script to make sure your MySQL installation is secure.  Unfortunately, the script is interactive and prompts for the root password, so it can't easily be included in the build process.  I tried analyzing the script and including the key parts in common/conf/mysql:

# cat common/conf/mysql

#!/bin/sh -e

set ${FAB_HOSTNAME:=backstage}

[ "$MYSQL_PASS" ] && /usr/lib/inithooks/bin/mysqlconf.py --pass="$MYSQL_PASS"

# start mysql server
/etc/init.d/mysql start

# secure mysql installation
mysql --defaults-extra-file=/etc/mysql/debian.cnf <<EOF
USE mysql;
# remove fabricating systems hostname from user table
DELETE FROM mysql.user WHERE Host = '$FAB_HOSTNAME';

# remove anonymous users
DELETE FROM mysql.user WHERE User='';

# remove remote root
DELETE FROM mysql.user WHERE User='root' AND Host NOT IN ('localhost', '127.0.0.1', '::1');

# remove test database
DROP DATABASE IF EXISTS test;
DELETE FROM mysql.db WHERE Db='test' OR Db='test\\_%';

# reload privilege tables
FLUSH PRIVILEGES;
EOF

# stop mysql server
/etc/init.d/mysql stop

At first I thought the modified script was not working, but after furthur tests, I realized the failure was due to a bug in my test procedure.  I'm testing using ProxMox virtual hosts.  I was just overwriting the test iso without changing the filename.  I forgot that if the VM has the iso attached, it keeps the file open so that overwriting does not actually replace the contents of the file.  I have to detach the iso and then reattach it every time the iso is changed.  I will conduct some additional tests and then submit a pull request.