Attach a server to Read-Only domain controller account using the Windows interface (Server 2008)

1. Log on as local Administrator to the server that will become the RODC, and then open a command prompt.
2. Type the following command, and then press ENTER:
   dcpromo /UseExistingAccount:Attach
3. On the Welcome to the Active Directory Domain Services Installation Wizard page, click Next, or, if you want to install from media or identify the source domain controller for AD DS replication, select the Use advanced mode installation check box.
4. On the Network Credentials page, type the name of any existing domain in the forest where you plan to install the additional domain controller, as shown in the following figure. Under Specify the account credentials to use to perform the installation, click Alternate credentials, and then click Set. In the Windows Securitydialog box, provide the user name and password for an account that was delegated the ability to install and administer the RODC when the RODC account was created. When you are finished providing credentials, click Next.
   
5. On the Select Domain Controller Account page, confirm that the wizard has found an existing RODC account that matches the name of the server, and then clickNext.
6. If you selected advanced installation mode, you can specify the following advanced options:
   1. On the Install from Media page, you can provide the location of installation media to be used to create the domain controller and configure AD DS or you can choose to have all data replicated over the network. Note that some data will be replicated over the network even if you choose to install from media. For information about using this method to install the domain controller, see Optional: Install RODC from media.
      
   2. On the Source Domain Controller page, you can specify a domain controller from which to replicate the configuration and schema directory partitions (or the entire Active Directory database if you do not choose to install from media). If you select This specific domain controller, you can select the domain controller that you want to provide source replication to create the new domain controller, and then click Next.
      
7. On the Location for Database, Log Files, and SYSVOL page, type or browse to the volume and folder locations for the database file, the directory service log files, and the system volume (SYSVOL) files, and then click Next.
   Windows Server Backup backs up the directory service by volume. For backup and recovery efficiency, store these files on separate volumes that do not contain applications or other nondirectory files.
8. On the Directory Services Restore Mode Administrator Password page, type and confirm the restore mode password, and then click Next. This password is used to start AD DS in Directory Service Restore Mode for tasks that must be performed offline. The password complexity and length must comply with the domain security policy.
9. On the Summary page, review your selections. Click Back to change any selections, if necessary.
   To save the settings that you selected to an answer file that you can use to automate subsequent AD DS operations, click Export settings. Type a name for your answer file, and then click Save.
   When you are sure that your selections are accurate, click Next to install AD DS.
10. You can either select the Reboot on completion check box to have the server restart automatically or you can restart the server to complete the AD DS installation when you are prompted to do so.