Unpacking the update.
Could not copy files.
Installation Failed.

After a bit of Googling I found a thread in the WordPress forums that contained a gem of a fix:

In the file /wp-admin/includes/class-wp-upgrader.php change this:

// Copy update-core.php from the new version into place.
if ( !$wp_filesystem->copy($working_dir . '/wordpress/wp-admin/includes/
  update-core.php', $wp_dir . 'wp-admin/includes/update-core.php', 
  true) ) {

To:

// Copy update-core.php from the new version into place.
if ( !$wp_filesystem->copy($working_dir . '/wordpress-mu/wp-admin/includes/
  update-core.php', $wp_dir . 'wp-admin/includes/update-core.php', 
  true) ) {

And low and behold: my automatic upgrade worked at once.

Upgrading issues with WordPress MU is a post by Joost de Valk on Yoast - Tweaking Websites.A good WordPress blog needs good hosting, you don't want your blog to be slow, or, even worse, down, do you? Check out my thoughts on WordPress hosting!

Migration of the data

We got a bit lucky in this project: the client had his own technical guy, who had written the previous platform himself and was willing to write a WXR exporter, so we could reasonably easily import all the posts through WXR. The issue was that some of these WXR files were about 20 MB large though, and the "normal" upload method of importing WXR's turned out to be fairly unstable.

Which is why I wrote a new Importer, based on the default WordPress import class:

This new Importer allows you to browse the local filesystem, and pick a WXR file to import:

This new Importer turned out to be a huge blessing in the process of importing 30 something blogs with a total of 29,019 posts and 46,319 comments. I'm not currently planning on releasing this importer, because of the huge amount of support that would take which I simply don't have time for.

Site wide posts and comments

Another thing that was needed on this site was a global index of all posts and comments. This was when I really found the WPMU Dev Premium package to be worth its money. The Post indexer and Comment Indexer plugins they have are really easy to use, and give you a global table you can easily query on.

Another one of their plugins that's really cool is the XML Sitemap plugin they offer, which generates an XML sitemap for every single blog. All I had to do was drop in a couple of files into a few directories and add one line to my .htaccess, how cool is that?

James Farmer of WPMU Dev has already agreed to be a guest on the upcoming podcast, so you'll hear more of these guys soon!

If you have a blog or blog network you'd like to migrate to WordPress MU, check out our WordPress Consulting services!

A Migration to WordPress MU is a post by Joost de Valk on Yoast - Tweaking Websites.A good WordPress blog needs good hosting, you don't want your blog to be slow, or, even worse, down, do you? Check out my thoughts on WordPress hosting!

For this project I needed some fairly simple things, that I could have used other plugins for but I wanted them to be simpler and cleaner than most plugins could do for me. One of those things was I needed to show an image for each post on the index and archive pages, if there was one, and wanted to be able to add a certain class to that.

So I wrote a small plugin called WordPress MU Attached Image, which does just that. It's use is simple, you download the attached image plugin, upload it to your mu-plugins folder, and use this in the loop in your theme:

yst_thumb('class','alt text');

Or, as in my case:

yst_thumb('alignright',get_the_title());

Now this plugin will work in a normal WordPress install too, but that's not what I wrote it for :)

Another thing I badly wanted was a plugin that would force the same permalink structure on all new blogs, and disallowed blog admins from changing them. This plugin does that, and immediately shows why I love WordPress MU development: the power it has to easily change things on tons of blogs at the same time is very cool.

It works like this: you download the fixed permalink plugin, make sure that on line 11, this reflects the permalink structure you want:

$yst_permalink_structure = '/%postname%/';

And you upload it to your mu-plugins folder. Voila: you're now the only one who can change permalink structures, and all new blogs will automatically have the right permalink structure.

You can expect more posts on WordPress MU in the coming weeks, as I dive deeper into the system. In the mean while, if you have a WordPress MU development project you'd like us to take on, contact me!

WordPress MU development, I love it! is a post by Joost de Valk on Yoast - Tweaking Websites.A good WordPress blog needs good hosting, you don't want your blog to be slow, or, even worse, down, do you? Check out my thoughts on WordPress hosting!