Former WordPress MU (WPMU) is now known as WordPress Multisite in version 3.0. This feature is not activated by default, you must enable it manually. The Multiuser function, lets you create a network of sites. You can run and host many different blogs with the same installation of WordPress. You must have web server file access to activate it. The instructions to activate Multisite are easy to follow and you should be able to get your installation activated with just 10 minutes work.
Start activating the multi-site features of WordPress 3.0 by adding this line of code to your wp-config.php file:
/** Enable or disable Worpress Multi-site features **/ define('WP_ALLOW_MULTISITE', true);
Refresh your Dashboard and got to ”Tools -> Network”. You will see a screen that looks similar to the one in the picture below:
If you want to install your additional blogs on virtual sub-domains instead of sub-directories you will need to create a wildcard DNS record on your server to enable the sub-domain (blog1.yourdomain.com, blog2.yourdomain.com, blog3.yourdomain.com) functionality of WordPress 3.0.
Your server must support wildcard DNS records for you to do this. As an example I will explain how to configure it with Hostgator. It’s very easy to do with the Hostgator Baby Plan allows them. When you are in your Hostgator Control Panel, follow these instructions to create a wildcard DNS record for a domain.
Select “sub-domains” under”Domains” in CPanel
Enter an asterisk “*” in the sub-domain’s name field
Select the TLD the wildcard DNS is to be set up on
Enter the server location address for the wildcard folder, e.g. /public_html/bigbuz
Back to your WordPress admin panel, you need to install the now activated WordPress 3.0 Network settings, viz
Find the Network settings page in your WordPress admin panel (Tools>Network)
Choose whether you want to use sub-domains or sub-folders for the additional blogs
Type a name for your network of sites
Set your admin email address
After a minute or two you will be presented with a configuration screen. Back up your .htaccess and wp-config.php files before you proceed to follow the instructions provided on that configuration screen.
As a precautionary measure to prevent visitors of non-existent sites from being greeted by 404 error messages, redirect them to a URL of your choice by adding the below code to the bottom your wp-config.php file:
/* Send visitors to non-existent blogs here */ define( 'NOBLOGREDIRECT', 'http://yourdomain.com/' );
Change http://yourdomain.com to the URL of your choice
Log out then log back in.
You will now need to go through your settings to enable or disable the new options provided by WordPress Multi Site.
Upgrading from WPMU to WordPress Multisite 3.0
If you are upgrading from WPMU to WordPress Multisite 3.0, you can do it automatically from the dashboard, but some manual configuration is also needed. After you upgrade and you login again into the dashboard, this message will be displayed:
Warning! WordPress encrypts user cookies, but you must add the following lines to wp-config.php for it to be more secure.
Follow the steps listed there and then you could see something like this:
“Thank you for Updating! Please visit the Update Network page to update all your sites.”
Follow the link and update all the blogs. (If you have any). Update Network.
Also you could see the following message:
“The wp-content/blogs.php file is deprecated. Please remove it and update your server rewrite rules to use wp-includes/ms-files.php instead.”
So, just remove the blogs.php file from the server and edit your .htaccess file. The .htaccess file can be found in the root folder, where the wp-config.php file is.
Open with notepad and change:
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-content/blogs.php?file=$2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]
Done! Your new Multiuser 3.0 installation is ready to use.