Edit the MySQL configuration file, /etc/my.cnf, and add some lines to the [mysqld] section, as follows:

[mysqld]
(...existing stuff...)
key_buffer = 16M
table_cache = 128
sort_buffer_size = 2M
myisam_sort_buffer_size = 8M
query_cache_size = 16M 

Now, we need to run some commands to run to get MySQL initialize. Don't type the prompts. Pick your own password for MySQL.

$ su -
# chkconfig mysqld on
# service mysqld start
# mysql -u root mysql
mysql> UPDATE user SET Password=PASSWORD('password') WHERE user='root';
mysql> FLUSH PRIVILEGES;
mysql> quit
# exit
$ mysql -u root -p < /usr/share/doc/mythtv-0.20/database/mc.sql

Now run the MythTV setup program. Do this as a regular user (not root). Command is: mythtv-setup