Specify user account name when adding a DC to an existing Forest

When the following error is prompted “You must specify user account name when adding a DC to an existing Forest”. This is because, when adding a new Domain Controller (DC) to an existing Active Directory (AD) forest. You must provide the credentials of a user account with sufficient privileges. Please see Active Directory: How to Setup a Domain Controller, how to access shared resources from two different domains, and how to install and configure Active Directory Domain Services on Windows Server 2022.

Note: This account must be a member of the Enterprise Admins group within the forest. Or Domain Admins (in the target domain) is used in adding a DC to a child domain. You could also delegate the permission as well.

Also, see “Enter connection information for your on-premise directory or forests: Azure AD connect unable to connect directory, forest not available. Here is a guide on ‘Active Directory Forest – Trees and Domain and Sites“.

Adding DC to Existing Forest: User Account Name Error Fix

As discussed above, the problem here was that Windows refused to use the default administrators credential.

Solution

Created a new user account in the domain, and add the user as a Domain administrator or Enterprise Administrator group. This will resolve the issue.

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