In a Windows domain environment, where is the main Active Directory database file (NTDS.dit) stored by default on a domain controller?

Introduction / Context:
Active Directory is the directory service used in many Windows based enterprise networks. It stores information about users, computers, groups and other objects in a database. Administrators who manage domain controllers should know where this core database file resides on disk. This question focuses on the default location of the Active Directory database on a Windows domain controller.

Given Data / Assumptions:

• We are working with Windows Server domain controllers, not client editions.
• The Active Directory database is stored in a file called NTDS.dit.
• The question asks about the default path used during typical installations.

Concept / Approach:
When you promote a Windows server to a domain controller using standard settings, the system creates an NTDS folder under the system root directory, which is often C:\\Windows. Inside that NTDS folder, it stores the main database file NTDS.dit along with related log files. Administrators can choose different paths during advanced installations, but the recommended and default location is %SystemRoot%\\NTDS. Understanding this path is important for backup, restore and troubleshooting procedures.

Step-by-Step Solution:
Step 1: Recall that the Active Directory database file is called NTDS.dit.Step 2: Remember that by default this file is placed in a folder named NTDS under the system root on the domain controller.Step 3: The environment variable %SystemRoot% usually points to C:\\Windows on a typical installation.Step 4: Option A states that the database is in %SystemRoot%\\NTDS as NTDS.dit, which matches the standard default.Step 5: Options B, C and D mention user folders, client workstations or external drives, none of which are correct for the main directory database.

Verification / Alternative check:
On an actual domain controller, if you browse to C:\\Windows\\NTDS, you can see NTDS.dit and several log and checkpoint files. Documentation on Active Directory backup and recovery also references this path and file name. While administrators may move the database to different volumes for performance or capacity reasons, the default location in training materials and exams remains %SystemRoot%\\NTDS.

Why Other Options Are Wrong:
Option B suggests that the database is stored inside a domain administrator user profile, which would not be secure or manageable. Option C claims that each workstation holds the full database in a temporary folder, which does not reflect the centralised design of Active Directory. Option D describes storage on an external USB drive as mandatory, which is not a standard or supported requirement for domain controllers.

Common Pitfalls:
New administrators sometimes confuse the SYSVOL folder, which stores policies and logon scripts, with the NTDS folder, which stores the Active Directory database. Another pitfall is assuming that client machines hold complete copies of the directory database; while clients cache information, the authoritative database is on domain controllers. For exam questions, always associate NTDS.dit with the %SystemRoot%\\NTDS directory on domain controllers.

Final Answer:
In the %SystemRoot%\\NTDS folder on the domain controller, typically as the file NTDS.dit.