Upgrading from WPMU to WP 3.0

administrator • 1st Jul 2010 • website design

Now that 3.0 is officially released, you may have seen an upgrade notice in the backend of your WPMU install. While the process is generally just clicking the upgrade button, there are a couple of additional steps to fully smooth out any merged changes that occurred.

First, backup your database(s) and the entire wp-content folder. Then hit the Upgrade button.

You’ll notice immediately after doing the auto-upgrade that there’s a yellow message in the admin area that states the following:

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, go ahead via ftp or through your web hosts control panel and delete the blogs.php file from the /wp-content/ folder. It’s been moved and renamed to /wp-includes/ms-files.php for you already.

You’ll now need to update your .htaccess file so your uploaded images will continue to display properly for your users. Find the line that says:
RewriteRule ^(.*/)?files/(.*) wp-content/blogs.php?file=$2 [L]
and change it to this:
RewriteRule ^(.*/)?files/(.*) wp-includes/ms-files.php?file=$2 [L]
You will also need to add a nonce salt to wp-config.php. You’ll get a warning about it and it will look similar to this:
define( 'NONCE_SALT', '6xF{&bvT_PAsmbnG<72.dJH>D8R8M!M{~r.U]-~j:rG!g!0(g7hvz)+/h9 IY7Ge' );
Stuff it in there with your other salts.

If you decide to upgrade manually, replacing the new files, make sure you snag the new TwentyTen default theme, as well as make the above changes. Feel free to finally dump Kubrick & Classic.

One of the things you will instantly notice is the renaming of the menus. Now that you’ve completed the basic upgrade, make sure your entire network gets updated by visiting the Super Admin -> Update page. As before, this will step through the blogs (now sites) a chunk at a time, applying any needed database changes.

Additional notes:
Since you are upgrading from WPMU, you are already running a network of sites. Please DO NOT follow the Create a Network instructions, as you will not need them.

If you’re running our multi-site plugin, no worries! It has worked smoothly for us and reportedly others who have upgraded MU.

In case you are running a version of WPMU earlier than the 2.9 branch, please step through upgrades manually to 2.9.x as outlined in the codex. Then you can continue as above.