Adding a Windows Server 2012 Essentials server to an existing domain, without migrating the AD

I have an existing Active Directory in house, a mix between a Win2K8R2 and Win2K3 domain, and i would like to test out Windows Server 2012 Essentials BETA on the network. When walking though the install, it gives me the option of a new domain, or migrating from an existing domain. when clicking existing, it tells me i can only have one SBS server running on a domain at a time... So, i dont have any existing SBS servers in house (both are full standard or enterprise editions) but i do plan on keeping at least one of these extra servers running... So, how do i get a 2012 Essentials server to join a domain, and not migrate the existing domain? or if i do migrate, can i still get one of the other boxes to act as secondary controllers?

This is an old question about beta but the same idea applies to RTM as well.

I just did this, and here's the situation. You can choose to migrate or create a new domain - if you migrate, and the source is NOT SBS but a normal AD environment, everything is happy (this is documented for example here: http://blogs.technet.com/b/sbs/archive/2012/08/24/migrating-to-windows-server-2012-essentials.aspx). (If it is SBS or EBS there are special rules around decommissioning the old server, etc.)

The only hiccup was the new environment didn't know anything about my users in the old environment. This is a documented issue with an easy fix: http://technet.microsoft.com/en-us/library/gg186128.aspx

1. On the Destination Server, open a Command Prompt window as an administrator.
2. Type cd "\Program Files\Windows Server\Bin", and press ENTER.
3. Type WssPowerShell.exe, and then press ENTER.
4. Type Import-WssUser -SamAccountName <username>, and then press ENTER.

I'm not finding good documentation about this from Microsoft, but based on the error messages you're seeing in the beta product still referencing Small Business Server (SBS) I am going to answer on the basis of how the SBS product operates.

You will need to migrate, demoting the current domain controller (DC) to a member server and transferring the Active Directory Flexible Single-Master Operation (FSMO) roles to the new DC. Once you've done that you can re-promote the existing machine back to being a secondary DC for the domain.

The limitation in SBS has, historically, been on having multiple Windows Server SBS machines. You can only have one. You can have as many secondary DCs as you want, however.

Having said all that, I'd be really concerned with migrating a production Active Directory domain onto a beta platform. Hopefully this is just a test lab that you're working with.

As the installer already tells you, no, you cannot run more than one Domain Controller when the existing Domain Controller is SBS.

This also obviously limits its use for inclusion into an existing domain.