I have multiple sites created by multiple users on my Omkea S install, and one of my users somehow deleted all of the content from his site. Is there a way to restore just one site without affecting any of the other sites, some of which have probably had changes since the incident?
It’s possible, as long as you have a backup, but you’d have to get a little bit into the weeds of the database to do so.
The content of a site is stored in the site table as well as several other tables starting site_ (plus item_site in Omeka S 3). You can dump only one site, and only the pages for that site, and only the blocks for those pages, etc, and just restore those without disturbing other sites.