The CASL Ambassadors web site is actually a collection of WordPress blogs – the main site plus one for each of six age group teams. When I initially set it up I tried using WordPress-MU but my hosting solution wasn’t capable for MU’s requirements. Then I tried a plugin called WP-Hive which allows a collection of blogs to share some common infrastructure. Wp-Hive looked promising but I ran into some concerns which kept me from using it.
Ultimately I ended up setting up a separate blog for each site and hoped to come back to it at some point. That point was a couple weeks ago when I decided to do some maintenance on the sites. I ended up using the main installation as a parent and linked (using Unix symbolic links) all of the sub-domain sites back to parent. The only exception was the wp-content directory which is a real directory (so uploads can be unique) but within wp-content I linked back to the parent’s themes and plugins.
This worked pretty well – if I install a plugin or theme for the main site it is available for all of the sub-domain sites and when I upgrade WordPress, all of the sub-domain sites are upgraded as well. Once I got this running, I wanted to share the users across all blogs.
After several attempts and numerous Google searches, I ended up following the directions in this thread and this thread and got everything to work. I don’t particularly care for having to modify one of the core WordPress files since it will go away the next time I update WordPress but none of the other solutions I tried worked.