I would like to share some of the Windows Active Directory Interview Questions and answers, will start with basic questions and continue with L1, L2, L3 level questions
What is Active Directory?
Active Directory (AD) is a directory service developed by Microsoft and used to store objects like User, Computer, printer, Network information, It facilitates to manage your network effectively with multiple Domain Controllers in different location with AD database, able to manage/change AD from any Domain Controllers and this will be replicated to all other DC’s, centralized Administration with multiple geographical locations and authenticates users and computers in a Windows domain
What is LDAP and how the LDAP been used on Active Directory(AD)?
What is Tree?
The tree is a hierarchical arrangement of windows Domain that share a contiguous namespace
What is Domain?
Active Directory Domain Services is Microsoft’s Directory Server. It provides authentication and authorization mechanisms as well as a framework within which other related services can be deployed
What is Active Directory Domain Controller (DC)?
Domain Controller is the server which holds the AD database, All AD changes get replicated to other DC and vise vase
What is Forest?
Forest consists of multiple Domains trees. The Domain trees in a forest do not form a contiguous namespace however share a common schema and global catalog (GC)
What is Schema?
Active Directory schema is the set of definitions that define the kinds of object and the type of information about those objects that can be stored in Active Directory
Active Directory schema is Collection of object class and there attributes
Object Class = User
Attributes = first name, last name, email, and others
Can we restore a schema partition?
Tell me about the FSMO roles?
Domain Naming Master
Schema Master and Domain Naming Master are the forest-wide roles and only available one on each Forest, Other roles are Domain-wide and one for each Domain
AD replication is multi-master replication and change can be done in any Domain Controller and will get replicated to others Domain Controllers, except above file roles, this will be flexible single master operations (FSMO), these changes only be done on dedicated Domain Controller so it’s single master replication
How to check which server holds which role?
Netdom query FSMO
Which FSMO role is the most important? And why?
Interesting question which role is most important out of 5 FSMO roles or if one role fails that will impact the end-user immediately
Most armature administrators pick the Schema master role, not sure why maybe they though Schema is very critical to run the Active Directory
Correct answer is PDC, now the next question why? Will explain role by role what happens when an FSMO role holder fails to find the answer
Schema Master – Schema Master needed to update the Schema, we don’t update the schema daily right, when will update the Schema? While the time of operating system migration, installing a new Exchange version and any other application which requires extending the schema
So if are Schema Master Server is not available, we can’t able to update the schema and no way this will going to affect the Active Directory operation and the end-user
Schema Master needs to be online and ready to make a schema change, we can plan and have more time to bring back the Schema Master Server
Domain Naming Master – Domain Naming Master required to creating a new Domain and creating an application partition, Like Schema Master we don’t create Domain and application partition frequently
So if are Domain Naming Master Server is not available, we can’t able to create a new Domain and application partition, it may not affect the user, user event didn’t aware Domain Naming Master Server is down
Infrastructure Master – Infrastructure Master updates the cross-domain updates, what really updates between Domains? Whenever user login to Domain the TGT has been created with the list of access user got through group membership (user group membership details) it also contain the user membership details from trusted domain, Infrastructure Master keep this information up-to-date, it update reference information every 2 days by comparing its data with the Global Catalog (that’s why we don’t keep Infrastructure Master and GC in the same server)
In a single Domain and single Forest environment, there is no impact if the Infrastructure Master server is down
In a Multi-Domain and Forest environment, there will be impact and we have enough time to fix the issue before it affect the end-user
RID Master –Every DC is initially issued 500 RID’s from RID Master Server. RID’s are used to create a new object on Active Directory, all new objects are created with Security ID (SID) and RID is the last part of a SID. The RID uniquely identifies a security principal relative to the local or domain security authority that issued the SID
When it gets down to 250 (50%) it requests the second pool of RID’s from the RID master. If RID Master Server is not available the RID pools unable to be issued to DC’s and DC’s are only able to create a new object depends on the available RID’s, every DC has anywhere between 250 and 750 RIDs available, so no immediate impact
PDC – PDC required for Time sync, user login, password changes, and Trust, now you know why the PDC is important FSMO role holder to get back online, PDC role will impact the end-user immediately and we need to recover ASAP
The PDC emulator Primary Domain Controller for backward compatibility and it’s responsible for time synchronizing within a domain, also the password master. Any password change is replicated to the PDC emulator ASAP. If a login request fails due to a bad password the login request is passed to the PDC emulator to check the password before rejecting the login request.
Tel me about Active Directory Database and list the Active Directory Database files?
Res1.log and Res2.log
All AD changes didn’t write directly to NTDS.DIT database file, first write to EDB.Log and from the log file to the database, EDB.Che used to track the database update from the log file, to know what changes are copied to the database file.
NTDS.DIT: NTDS.DIT is the AD database and stores all AD objects, the Default location is the %system root%\nrds\nrds.dit, Active Directory database engine is the extensible storage engine which is based on the Jet database
EDB.Log: EDB.Log is the transaction log file when EDB.Log is full, it is renamed to EDB Num.log where num is the increasing number starting from 1, like EDB1.Log
EDB.Che: EDB.Che is the checkpoint file used to trace the data not yet written to database file this indicates the starting point from which data is to be recovered from the log file in case if failure
Res1.log and Res2.log: Res is reserved transaction log file which provides the transaction log file enough time to shut down if the disk didn’t have enough space
What RAID configuration can be used in Domain Controllers?
Can we keep OS, log files, SYSVOL, AD database on same logical Disk?