I've been putting off setting up multisite on my localhost for ages, mostly because in the past I've found getting Apache virtual hosts to work can be a bit tricky: not impossible, but the sort of thing where I could easily lose an hour on a minor thing I've forgotten to do. And after all, with a shiny new iMac and a hard drive whose proportions I can't even remember, why not just 'drush dl' all over again?

But I'm actually working on a multisite project at the moment, and suddenly getting this to work becomes more interesting than having another SVN copy of my code kicking around.

Given multisite can respond to subfolders, I was wondering if this could work when Drupal itself is in a subfolder, like this:

Turns out it can. Suppose you want a new subsite called 'drupal-subsite'. Here's what to do in your webroot:

Your lolcathost(*) sees just another subfolder that's a site; the symbolic link sends you to the existing Drupal folder; and finally, the multisite system sees that you're browsing 'localhost/drupal-subsite' and selects the localhost.drupal-subsite folder as the one holding your site.

You can also have your subsite explicitly sit below the main site like this:

In which case your sites folder is localhost.drupal-multisite.drupal-subsite and the symlink should be inside the multisite folder:

So when I next get a moment I'll consolidate the various test sites I have, and when I have more than one patch on the go that I want to keep segregated, I can just add a multisite, get a fresh CVS copy of the code, and get going.

I've added details to the documentation too.

(*) yes, I keep typing it like that.