I did the following steps and so far so good:
1. install Bitnami WordPress stack
2. edit Apache2 httpd.conf and make document root point to .../apps/wordpress/htdocs/
3. set directory in httpd.conf as follow:
Alias /wordpress/ "/opt/www/apps/wordpress/htdocs/"
Alias /wordpress "/opt/www/apps/wordpress/htdocs"
<Directory "/opt/www/apps/wordpress/htdocs/">
Options Indexes MultiViews +FollowSymLinks
AllowOverride All
Order allow,deny
Allow from all
RewriteEngine On
RewriteBase /opt/www/apps/wordpress/htdocs/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^/$ /opt/www/apps/wordpress/htdocs/ [PT]
</Directory>
4. comment out the Include of "...wordpress.conf"
5. edit wp-config.php and add the following lines after
<?php
define('WP_ALLOW_MULTISITE', true);
define('WP_HOME','http://mysite.com');
define('WP_SITEURL','http://mysite.com');
6. test on mysite.com and everything works fine
7. upgrade to wordpress 3.3.1 and 6 other default plugins and I can still use mysite.com directly access my site at root
8. activate network mode
9. follow the instructions by copying codes to wp-config.php and .htaccess with
define( 'MULTISITE', true );
define( 'SUBDOMAIN_INSTALL', true );
$base = '/';
define( 'DOMAIN_CURRENT_SITE', 'meetsky.com' );
define( 'PATH_CURRENT_SITE', '/' );
define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 1 );
and