Unbind from a server
If a computer is using Directory Utility’s Active Directory connector to bind to an Active Directory server, you can unbind the computer from the Active Directory server.
You can forcibly unbind if the computer can’t contact the server or if the computer record is removed from the server.
Click the lock icon.
Enter an administrator’s user name and password, then click Modify Configuration (or use Touch ID).
Select Active Directory, then click the Edit button (looks like a pencil).
Click Unbind, authenticate as a user who has rights to terminate a connection to the Active Directory domain, then click OK.
If you see an alert saying the credentials weren’t accepted or the computer can’t contact Active Directory, click Force Unbind to forcibly break the connection.
If you forcibly unbind, Active Directory still contains a computer record for this computer. Let the Active Directory administrator know to remove the computer record.