How to migrate multiple blogs into WordPress 3.0

While the Multi-Site feature of WordPress 3.0 can run a network of multiple blogs, how to get there from existing WordPress blogs running on separate installations into one installation has been quite a learning process.

This blog post a place to share how I’m doing it, and please do add a comment as you learn how to do the export + import to merge your blogs together into one. These are the main steps, and may not include every single detail that may be required in your specific instance, since every web host setup may be different & unique.

1. Install WordPress 3.0 onto a web server. I made a brand new installation from scratch. (I’m using an independent hosted web server.)
2. Turn on the “multi-site” feature to create a network for multiple blogs. (e.g. define WP_ALLOW_MULTISITE in wp-config.php; I used a “subdirectories” install.)
3. Manually install the WordPress MU Domain Mapping plugin – use the trunk version(!) for 3.0 compatibility. Put sunrise.php and domain-mapping.php into the right directories. Activate plugin.
4. Enable domain mapping using instructions at WordPress 3.0: Multisite Domain Mapping Tutorial as a reference (the exact details didn’t fit my server configuration)
5. Install the WordPress importer in the 3.0 blog (Dashboard> Tools> Import> WordPress )
6. For each existing blog, do these steps:
   • Add a new sub-site in the 3.0 blog for the existing blog (Dashboard> Super Admin> Sites> Add New )
   • Export content from the existing blog (Dashboard> Tools> Export)
   • Login to the backend of the new sub-site, and then import the .XML file via the 3.0 blog’s import function (Dashboard> Tools> Import> WordPress ) [cf. alternative way to migrate is to export from the old blog’s database tables and import directly into the new 3.0 blog’s database]
   • Map the existing blog’s domain name to the sub-site (Dashboard> Super Admin> Domains> New Domain ) *
   • Edit the site info for each individual blog to map an existing domain in the 3.0 config (Dashboard> Super Admin> Sites > Edit ) *
   • * Somewhere along the way, you may need to change the domain DNS info or something, and this is the step I haven’t figured out yet
7. Now you’ve got content from existing multiple blogs migrated into one 3.0-powered blog. With WordPress 3.0 being so new, many themes and plugins may not be compatible. So, if your most concerned about getting content consolidated, the above procedure may be the way to go. If you want customized functionality and customized design, separate WordPress installs may be better.

Other articles that may be helpful:

• Enabling WordPress 3.0 Multisites on GoDaddy
• According to this article about DreamHost, “Multi-Site is not supported on our shared servers. You will need a PS to enable the feature. You will also need wildcard DNS which also requires a PS.”
• Installing WordPress on Hostgator
• Can I import multiple standalone blogs into 3.0? [issue re: domain mapping]
• Multiple installs/blogs upgrade to 3.0 multisite
• WP3 Multi Blogs Questions
• WordPress 3.0 Multisite With Multiple Domains Setup [interconnectit.com]