In my pervious Article, I have explained how to install First Domain Controller in new Forest. Here I will guide how to promote secondary domain controller and also how to remotely promote it using Server Manager.
Open Server Manager, here I have added servers in Server Manager, Right Click on the server which you need to promote as Secondary Domain Controller and Click on Add Roles and Features,
Select Role-based or feature-based installation and Click Next,
Select Server and click Next,
Click on Add Features,
No need to select any features by default Group policy selected. Click Next,
Click Install to begin installation,
Click on Promote this server to a domain controller,
select add a domain controller to an existing domain and click on change to provide domain administrator account,
provide the credentials,
You can select DNS and GC if required this server to act as or you can leave if your primary is same site and enter the DSRM password. Click Next,
Select the DC from where you want to take replication or select Any Domain Controller, you also can install IFM if you have it with you to avoid Network bandwidth utilization, Click Next,
Review the Settings and Click Next,
Wait for sometime to get this completed,
That is it.. Server is successfully configured as domain Controller, You can close it and restart the server remotely.