Sometimes there is a requirement to run multiple different MySQL servers on the same FreeBSD host, this makes it possible to create profiles to run different MySQL servers with different database paths/settings.

mysql-server-multi

#!/bin/sh
#
# PROVIDE: mysql
# REQUIRE: LOGIN
# KEYWORD: shutdown
#
# Add the following lines to /etc/rc.conf to enable mysqlmulti:
#
# mysqlmulti_enable (bool):		Set it to "YES" to enable uwsgi
#				Default is "NO".
# mysqlmulti_limits (bool):	Set to "NO" by default.
#			Set it to yes to run `limits -e -U mysqlmulti`
#			just before mysqlmulti starts.
# mysqlmulti_dbdir (str):	Default to "/var/db/mysql"
#			Base database directory.
# mysqlmulti_pidfile (str):	Custum PID file path and name.
#			Default to "${mysqlmulti_dbdir}/${hostname}.pid".
# mysqlmulti_args (str):	Custom additional arguments to be passed
#			to mysqlmultid_safe (default empty).
# mysqlmulti_user (str):    User to start MySQL server as (default: mysql)
#
# If you would like to have multiple mysqlmulti instances running, you can
# define multiple profiles:
#
# mysqlmulti_profiles (str):		Set the list of mysqlmulti profiles
#				Default is "".
#
# For each profile you can then define different options (except for
# mysqlmulti_enable) using the syntax uwsgi_<profile>_<option>

. /etc/rc.subr

name="mysqlmulti"
rcvar=mysqlmulti_enable

load_rc_config $name

: ${mysqlmulti_enable="NO"}
: ${mysqlmulti_profiles=""}
: ${mysqlmulti_limits="NO"}
: ${mysqlmulti_dbdir="/var/db/mysql"}
: ${mysqlmulti_user="mysql"}

is_mysqlmulti_profile() {
    local profile

    for profile in $mysqlmulti_profiles; do
        if [ "$profile" = "$1" ]; then
            return 0
        fi
    done

    return 1
}

if [ -n "${mysqlmulti_profiles}" ]; then

	if [ -n "$2" ]; then
		profile="$2"
		if ! is_mysqlmulti_profile $profile; then
			echo "$0: no such profile defined in mysqlmulti_profile"
		        exit 1
		fi

		eval mysqlmulti_limits=\${mysqlmulti_${profile}_limits:-"${mysqlmulti_limits}"}
		eval mysqlmulti_dbdir=\${mysqlmulti_${profile}_dbdir:-"${mysqlmulti_dbdir}"}
		eval mysqlmulti_args=\${mysqlmulti_${profile}_args:-"${mysqlmulti_args}"}
		eval mysqlmulti_pidfile=\${mysqlmulti_${profile}_pidfile:-"${mysqlmulti_pidfile}"}
		eval mysqlmulti_user=\${mysqlmulti_${profile}_user:-"${mysqlmulti_user}"}

	elif [ -n "$1" ]; then
		for profile in ${mysqlmulti_profiles}; do
	            echo "Processing ${name} profile: ${profile}"
	            /usr/local/etc/rc.d/mysql-server-multi $1 ${profile}
	        done
	        exit 0
	fi
fi

mysql_limits_args="-e -U ${mysqlmulti_user}"
pidfile=${mysqlmulti_pidfile:-"${mysqlmulti_dbdir}/`/bin/hostname`.pid"}
command="/usr/sbin/daemon"
command_args="-c -f /usr/local/bin/mysqld_safe --defaults-extra-file=${mysqlmulti_dbdir}/my.cnf --user=${mysqlmulti_user} --datadir=${mysqlmulti_dbdir} --pid-file=${pidfile} ${mysqlmulti_args}"
procname="/usr/local/libexec/mysqld"
start_precmd="${name}_prestart"
start_postcmd="${name}_poststart"
mysql_install_db="/usr/local/bin/mysql_install_db"
mysql_install_db_args="--basedir=/usr/local --datadir=${mysqlmulti_dbdir} --force"

mysqlmulti_create_auth_tables()
{
	eval $mysql_install_db $mysql_install_db_args >/dev/null 2>/dev/null
        [ $? -eq 0 ] && chown -R ${mysqlmulti_user}:${mysqlmulti_user} ${mysqlmulti_dbdir}
}

mysqlmulti_prestart()
{
	if [ ! -d "${mysqlmulti_dbdir}/mysql/." ]; then
		mysqlmulti_create_auth_tables || return 1
	fi
	if checkyesno mysqlmulti_limits; then
		eval `/usr/bin/limits ${mysql_limits_args}` 2>/dev/null
	else
		return 0
	fi
}

mysqlmulti_poststart()
{
	local timeout=15
	while [ ! -f "${pidfile}" -a ${timeout} -gt 0 ]; do
		timeout=$(( timeout - 1 ))
		sleep 1
	done
	return 0
}

run_rc_command "$1"

rc.conf

mysqlmulti_enable="YES"
mysqlmulti_profiles="main second"
mysqlmulti_main_dbdir="/usr/db/main"
mysqlmulti_second_dbdir="/usr/db/second"

A similar patch can be found in an old FreeBSD bug report: http://www.freebsd.org/cgi/query-pr.cgi?pr=ports/171852

If your running multiple instance do not use an instance named "mysql" or others will get my.cnf from the default folder.
Other thing : Change listen port, path to socket for each instance ;)