If you have been testing out the beta of WordPress, and are new to the whole concept of multiple sites, you may have noted a lot of the wordpress-mu-specific plugins make reference to the mu-plugins folder.
This is not created by default. You must create it in the wp-content folder.
The “mu” does not stand for multi-user like it did for WPMU, it stands for “must-use” as any code placed in that folder will run without needing to be activated. An actual file has to be there; if all the files are in a subfolder, they will not be read.
You can now see the content of that folder in the backend, under the Plugins menu. When visiting, you’ll see a sub-item called “Must Use”, if you’ve created that folder and placed files within.


Short and well explained. I haven’t tested the “MU” plugin part of 3.0, yet, but this definitely will help with the logic behind it.
Thanks!
Great, and super helpful explanation! I was wondering how the mu-plugins folder was going to fit in.
Question:
Will Plugin Commander still be needed, or will this “activate plugin sitewide” be built-in?
Just out of curiosity, when do these plugins load? Could I use them to affect the way the wordpress environment loads entirely, such as to change the database connections specified in wp-config.php?
Prior to the regular plugins.
Hey there, I would also like to go and test wp 3.0. Is there a way to update from wpmu 2.9.2 to the wp 3.0 beta 1?
I’ve installed the wp beta tester plugin, which just does not work for that unfortunately. And I don’t really want to do it manually since I fear I could do something wrong…
Thanks
Manually.
This means overwriting the files you have with the zip from trac. Testing betas involves things breaking, so you have to get in and get dirty.
Use the Beta Tester plugin.
This is a little off topic, but is the current version of Plugin Commander still needed in 2.9.2? (as I notice I have option in 2.9.2 package to enable or disable a plugin site-wide).