How to run multiple sites on Wordpress 3.0 on separate domains

So we were eager to test the multi-site functionality of Wordpress 3.0 beta. While it’s not for the average end-user to toy around with and most may not even need this function, setting it up in not very difficult either. However our goal was to use the multi-site functionality on TLD (or stand-alone/add-on domains) and not on a sub-domain or sub-directory hierarchy. Here’s a step-by-step walkthrough. Please understand that this is not for the average wordpress user but for webmasters who know what they are doing and talk the jargon.

1. Setting up the domains

   This section will deal with configuring the domains.

2. Installing Wordpress

   This section will deal with configuring the wordpress installation.

3. Domain Mapping

   This section will deal with configuring the secondary sites on their own domain (instead of subdomain or subdirectory)

1. Setting up the domains:

   1. Setup your main domain. This may involve the basics like registering it, setting up the nameservers, setting up the hosting etc. Once you have the hosting setup and you are ready to upload the files, follow these steps before installing Wordpress.
   2. Let’s refer to your primary domain as www.primarydomain.com and let us refer to your secondary domain as www.secondarydomain.com.
   3. Wildcard DNS: Create a subdomain on your primarydomain.com called “*” (without quotes). This will make sure that <some-random-sub-domain>.primarydomain.com does not return a 404 error.
   4. Park your secondary domain: Add www.secondarydomain.com as a parked domain in your account.

2. Install Wordpress

   1. Install Wordpress 3 at www.primarydomain.com as instructed in the official documentation and setup your first site.
   2. Add the following line to your wp-config.php file define('WP_ALLOW_MULTISITE', true);
   3. In the wordpress admin section go to Tools > Network. Choose subdomains amongst sub-domains and sub-directories. Follow the instructions on the screen to finish the network setup.
   4. Once you finish the network setup you’ll have the Super Admin menu activated on the admin screen.
   5. Go to Super Admin > Sites. Add a new site (for the secondary domain). For now we’ll have to set it up as a subdomain and we’ll later map it to the main domain. Let’s create it as secondary.primarydomain.com.
   6. Browse to this site and verify that everything is fine.

3. Domain Mapping

   1. Download the wordpress-mu-domain-mapping plugin. Extract it to a temporaty folder.
   2. Upload sunrise.php to wp-content.
   3. Upload domain_mapping.php to wp-content/plugins/
   4. Edit wp-config.php and add define('SUNRISE','on'); and use the “Network Activate” option to activate it (find it on the plugins manager page).
   5. Set the server Ip address to the ip address of www.primarydomain.com (find that by pinging www.primarydomain.com).
   6. Log into http://secondary.primarydomain.com/wp-admin
   7. Go to Tools > Domain Mapping
   8. Under “Add new domain” enter secondarydomain.com and check “Primary Domain for this blog”. Click “Add”.
   9. Now your secondary site will be available at www.secondarydomain.com instead of secondary.primarydomain.com.

I hope you find these instructions helpful.