New server joined to an external domain

[Luisgp]

Hello, I am new to the forum, but not to Zentyal.

I am installing a new Zentyal 3.5 server and want to use it as a File Server for an existing domain. It is replacing an CentOS machine that was fulfilling te same role, so I am not new to Samba or Linux or Active Directory.

During setup, I joined the existing domain as external and now I cannot use the File services since the machine is not a domain controller. But there is no option in the GUI that I can find to turn it into a domain controller. The DOMAIN option is missing altogether, I can only see LDAP and USERS and GROUP (albeit as read-only).

So what do I need to do to turn the machine from domain member to domain controller and be able to share files folders?

Thank you for your input.