I've read though a lot of other posts on getting multisite setups working and on getting mod_rewrite working. I can get either one but not both. Here's my setup: I have hosting with 1and1, and my configuration looks kind of like this:
primary_domain_docroot
|
|
+-- cms
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+-- site1a.com/cms*
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+-- site2a.com/cms*
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+-- site3a.com/cms*
So primary_domain is a big long name that's no real use to me, but it's important because it means that all these directories can be served by Apache. The other sites are the ones I actually pay for and use, I believe the correct term for these is an 'add-on domain'. I've set each site to have its root at a directory with the same name as the site.
Each of the cms* items is a soft link back to primary_domain_docroot/cms, which corresponds to a real directory on the server. At the root of each of site1a.com, site2a.com and site3a.com (siteXa.com for short) I have an .htaccess file that just redirects to its own cms* softlink. That'd be primary_domain_docroot/site1a.com/.htaccess, for example. This in turn serves up the correct site. Of course each of these sites is configured under primary_domain_docroot/cms/sites/.../settings.php.
I also have an .htaccess at primary_domain_docroot/cms/.htaccess which handles clean urls properly as long as the urls are under siteXa.com/cms. To achieve this I use "RewriteBase /cms" in that .htaccess. All is well except that I have this extra /cms/ stuff at the start of all my urls.