If you have to host only 1 subdomain for a domain not present on your server, you can setup directly the whole domain path as "main domain".
- You want to host wiki.adomain.com but you does not handle adomain.com owned by a friend (who setup its DNS to point your server for the subdomain "wiki")
==> create wiki.adomain.com as domain in Sentora, not as subdomain.
If you have to host more than 1 subdomain for a domain not present on your server, you have to add the root domain in the "shared domain" list (Sentora -> Admin -> Module Admin -> Apache Config -> "Shared Domains" input box). But note that all Sentora accounts will be able to create subdomains of "shared domains".
- You want to host wiki.adomain.com AND docu.adomain.com but you does not handle adomain.com ... (etc)
==> add "adomain" (without ".com") in the "shared domains" list and then create both wiki.adomain.com and docu.adomain.com as domain (not subdomain).