Upgrading WordPress MU to WordPress 3.0

The various site on this server are powered by WordPress. Because there are multiple sites, I use WordPress MU (multi user). This fork of WordPress allows running multiple blogs from one installation, either in sub directories, or (in my case) on sub domains.

A couple of days ago WordPress 3 was released. WordPress MU is now integrated into WordPress. This is good news, because now there is only one WordPress, and I can easily upgrade to new versions, without having to wait for an updated WordPress MU version. But the first task, upgrade WordPress MU to WordPress 3.

There is a very handy auto update feature. You simply have to click a link and the update takes place, or so is the theory. That sort-of worked, but a few changes were needed. For the upgrade to succeed, the web server must have permission to write to the the directory where WordPress is installed. By default, I disabled this, and only allow writes to certain folder. Simple (temporarily) giving every one write access solved that problem:

chmod -R o+w wordpress/

After that, the upgrade went fine. A few things were needed to make everything work. First, I do not run Apache as a web server, but lighttpd. This makes permalinks and uploaded files a bit difficult. I have the following lighttpd config to make all this work:

url.rewrite-once = (
"^/(.*)?/?files/$" => "index.php",
"^/(.*)?/?files/(.*)" => "wp-includes/ms-files.php?file=$2",
"^/(wp-.*)$" => "$1",
"^/([_0-9a-zA-Z-]+/)?(wp-.*)" => "$2",
"^/([_0-9a-zA-Z-]+/)?(.*\.php)$" => "$2",
"(\?.*)$" => "index.php$1",
"." => "index.php"

And a few settings had to be added to the wp-config.php file. The following must be added:

define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', true);

The first setting tells WordPress that I run a “multisite”, what used to be the “MU”. The second option tells WordPress that each blog has its own subdomain, as opposed to its own sub directory. Without this last line, permalinks do no work, and all links are redirected to the main site (with no subdomain).

Other that that, the upgrade went pretty fine. Actually, I’m quite impressed with how easy the upgrade of WordPress.

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