You want to back up Active Directory to tape or disk.
Back up the System State, which includes the Active Directory-related files on the domain controller. Here are the directions for backing up the System State using the NtBackup utility that comes installed on Windows 2000 and Windows Server 2003 computers:
Go to Start All Programs (or Programs for Windows 2000) Accessories System Tools Backup.
Click the Advanced Mode link.
Click the Backup tab.
Check the box beside System State.
Check the box beside any other files, directories, or drives you would also like to back up.
For Backup destination, select either File or Tape depending on where you want to back up the data to.
For Backup media or file name, type either the name of a file or select the tape to save the backup to.
Click the Start Backup button twice.
The NtBackup utility supports several command-line parameters that you can use to initiate backups without ever bringing up the GUI.
For the complete list of supported commands on Windows 2000, see MS KB 300439 (How to Use Command Line Parameters With the "Ntbackup" Command).
For the complete list of supported commands on Windows Server 2003, see MS KB 814583 (HOW TO: Use Command Line Parameters with the Ntbackup Command in Windows Server 2003).
Fortunately, domain controllers can be backed up while online. Having the ability to do live backups makes the process very easy. And since Active Directory is included as part of the System State on domain controllers, you are required to back up only the System State, although you can back up other folders and drives as necessary. On a domain controller, the System State includes the following:
COM+ class registration database
Active Directory files
System Volume (SYSVOL)
Certificates database (if running Certificate Server)
Recipe 16.18 for modifying the tombstone lifetime, MS KB 216993 (Backup of the Active Directory Has 60-Day Useful Life), MS KB 240363 (HOW TO: Use the Backup Program to Back Up and Restore the System State in Windows 2000), MS KB 300439 (How to Use Command Line Parameters With the "Ntbackup" Command), MS KB 326216 (HOW TO: Use the Backup Feature to Back Up and Restore Data in Windows Server 2003), and MS KB 814583 (HOW TO: Use Command Line Parameters with the Ntbackup Command in Windows Server 2003)