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I want to make a website that uses the same joomla files but different websites for each subdomain. I figured this approach is best for a multi website installation. Each subsite is a simple site that frontend users can create/edit articles from certain categories or upload images and files (for download). Also the database content (users, articles, images) is not shared between subsites. The reason I want the same files is that so I can edit the template files all at once, for instance to manually insert a common banner for all websites. I know that if I want to install a plugin for all the sites, I will have to manually install and configure them on each subsite, but I see no alternative.
What I want to know if this is possible.
I am also opened for suggestions on different approaches. (If any extensions are involved I would preffer free ones.)