Which FSMO role is responsible for adding removing domain controller in Domain?

Domain Naming Master

What is the impact of Losing FSMO Role?

PDC Emulator (Domain Role)

Any Domain Controller performing an Operations Master (FSMO) function will not be the end of your environment; but each does have a potential for impact given a sufficient window of absence. In usual circumstances, however, the most crippling role to lose is the PDC Emulator.

In a mixed-mode environment, when the PDC Emulator goes down, you lose the bridgehead server for Windows NT 4.0 networks involved in trust relationships with that Active Directory domain. You also lose any down-level updating of the SAM for your Windows NT 4.0 Backup Domain Controllers, therefore Active Directory account changes such as password changes, login name changes etc. are never communicated.

Regardless of the mode or functional-level of the domain, you stand the risk of losing time-synch within the domain. The more complex and distributed the domain/forest, the greater the potential of Kerberos failures as the clocks fall apart from one-another on the Domain Controllers or clients which were directly dependent upon the defunct PDC Emulator.

Any Domain sitting above Mixed Mode would still also be susceptible to password changes not being communicated across the domain in a timely fashion.

RID Master (Domain Role)

If the Domain Controller performing as the RID Master goes down or becomes inaccessible, Windows 2000 and above domain controllers will have no place to acquire new RID pool assignments. As this function is only called upon sporadically , unless you are adding security principals in bulk, this outage may not become apparent for some time.

A more noticeable occurrence may be the failure of the movetree.exe command to function properly as it relies upon the RID Master present in the domain that the object is coming from to actually perform the move.

Infrastructure Master (Domain Role)

In the event that the Infrastructure Master Role holder is lost, the ramifications will vary based upon whether the forest is in itself a single domain, or if it contains multiple domains. If everything within your Active Directory forest is contained within a single domain, the Infrastructure Master really doesn’t have anything to do as there are no cross-domain references to be maintained.

In a forest with multiple domains, the Infrastructure Master Role holder plays a more vital role by maintaining cross-domain references (i.e. users from Domain A are members of a group in Domain B). Now the kicker here, any server in Domain B that is a Global Catalog Server will be automatically maintained due to the intercommunications of the GC processes forest-wide. This would make for an intermittent issue as some servers would have stale phantom references and others would be up-to-date.

Domain Naming Master (Forest Role)

If the Domain Naming Master role holder is lost, domains won’t be able to be added or removed from the Active Directory forest. DCPROMO is also affected, meaning that servers can neither be promoted nor demoted.

Though the loss of this role holder impacts some more common operations performed within an Active Directory forest and its contained domains, it is still doesn’t create highly visible issues within your environment.

Schema Master (Forest Role)

All Domain Controllers contain a copy of the Active Directory Schema. This Schema is essentially a template or listing of the various Active Directory object types and available attributes present within a given forest. This template is used to refresh the Active Directory database where the actual objects are stored.

The loss of the Schema Master Role holder in an Active Directory puts the forest into a state of stasis so no extensions (addition of object types and/or attributes) to the Schema can be made. This would impair activities such upgrading an Active Directory domain from Windows Server 2000 to Windows Server 2003, installing Microsoft Exchange, and/or adding new attributes to an object. All things considered, as this sort of activity does not happen on a daily basis, a forest could survive the loss of this role holder and continue with minimal inconvenience in most cases.

Brief all the FSMO Roles

A multi-master enabled database, such as the Active Directory, provides the flexibility of allowing changes to occur at any DC in the enterprise, but it also introduces the possibility of conflicts that can potentially lead to problems once the data is replicated to the rest of the enterprise. One way Windows deals with conflicting updates is by having a conflict resolution algorithm handle discrepancies in values by resolving to the DC to which changes were written last (that is, "the last writer wins"), while discarding the changes in all other DCs. Although this resolution method may be acceptable in some cases, there are times when conflicts are just too difficult to resolve using the "last writer wins" approach. In such cases, it is best to prevent the conflict from occurring rather than to try to resolve it after the fact.

To prevent conflicting updates the Active Directory performs updates to certain objects in a single-master fashion.

In a single-master model, only one DC in the entire directory is allowed to process updates. In a forest, there are five FSMO roles that are assigned to one or more domain controllers. The five FSMO roles are:

PDC Emulator FSMO Role

The PDC emulator is necessary to synchronize time in an enterprise. Windows includes the W32Time (Windows Time) time service that is required by the Kerberos authentication protocol. All Windows-based computers within an enterprise use a common time. The purpose of the time service is to ensure that the Windows Time service uses a hierarchical relationship that controls authority and does not permit loops to ensure appropriate common time usage.

The PDC emulator of a domain is authoritative for the domain. The PDC emulator at the root of the forest becomes authoritative for the enterprise, and should be configured to gather the time from an external source. All PDC FSMO role holders follow the hierarchy of domains in the selection of them in-bound time partner.

In a Windows domain, the PDC emulator role holder retains the following functions:

• Password changes performed by other DCs in the domain are replicated preferentially to the PDC emulator.

• Authentication failures that occur at a given DC in a domain because of an incorrect password are forwarded to the PDC emulator before a bad password failure message is reported to the user.

• Account lockout is processed on the PDC emulator.

• The PDC emulator performs all of the functionality that a Microsoft Windows NT 4.0 Server-based PDC or earlier PDC performs for Windows NT 4.0-based or earlier clients.

RID Master FSMO Role

The RID master FSMO role holder is the single DC responsible for processing RID Pool requests from all DCs within a given domain. It is also responsible for removing an object from its domain and putting it in another domain during an object move.

When a DC creates a security principal object such as a user or group, it attaches a unique Security ID (SID) to the object. This SID consists of a domain SID (the same for all SIDs created in a domain), and a relative ID (RID) that is unique for each security principal SID created in a domain.

The RID master gives every DC a pool of 500 RIDs at a time. When a new domain account or group is created, the DC assigns the new account a SID and a RID that's taken from its local allocated RID pool. When a DC's RID pool begins to run low (Pre–Windows 2000 SP4 20%, Post–Windows 2000 SP4 50%), it automatically asks the RID master for another block of RIDs. Therefore, a post–Windows 2000 SP4 DC with a default pool size of 500 requests a new pool when 250 RIDs have been consumed. To check the RID allocation with Dcdiag, type the following at a command prompt:

dcdiag.exe /test:ridmanager /v

Infrastructure FSMO Role

When an object in one domain is referenced by another object in another domain, it represents the reference by the GUID, the SID (for references to security principals), and the DN of the object being referenced. The infrastructure FSMO role holder is the DC responsible for updating an object's SID and distinguished name in a cross-domain object reference.

NOTE: The Infrastructure Master (IM) role should be held by a domain controller that is not a Global Catalog server(GC). If the Infrastructure Master runs on a Global Catalog server, it will stop updating object information because it does not contain any references to objects that it does not hold. This is because a Global Catalog server holds a partial replica of every object in the forest. As a result, cross-domain object references in that domain will not be updated and a warning to that effect will be logged on that DC's event log.

If all the domain controllers in a domain also host the global catalog, all the domain controllers have the current data, and it is not important which domain controller holds the infrastructure master role.

When the Recycle Bin optional feature is enabled, every DC is responsible to update its cross-domain object references when the referenced object is moved, renamed, or deleted. In this case, there are no tasks associated with the Infrastructure FSMO role, and it is not important which domain controller owns the Infrastructure Master role.

Domain Naming Master FSMO Role

The domain naming master FSMO role holder is the DC responsible for making changes to the forest-wide domain name space of the directory (that is, the Partitions\Configuration naming context or LDAP://CN=Partitions, CN=Configuration, DC=<domain>). This DC is the only one that can add or remove a domain from the directory. It can also add or remove cross references to domains in external directories.

Schema Master FSMO Role

The schema master FSMO role holder is the DC responsible for performing updates to the directory schema (that is, the schema naming context or LDAP://cn=schema,cn=configuration,dc=<domain>). This DC is the only one that can process updates to the directory schema. Once the Schema update is complete, it is replicated from the schema master to all other DCs in the directory. There is only one schema master per directory.

What are Active Directory Logical and Physical Components?

Active directory physical structure is a hierarchal structure which fallows

Forests -> Trees -> Domains -> Child Domains -> Grand Child etc.

Active directory is logically divided into partitions

• Configuration partition
• Schema Partition
• Domain partition
• Application Partition (only in windows 2003 not available in windows 2000)

What Are Lingering Objects?

When restoring a backup file, Active Directory generally requires that the backup file be no more than 180 days old. If attempt to you restore a backup that is expired, you may encounter problems due to “lingering objects”.

A lingering object is a deleted AD object that re-appears (“lingers”) on the restored domain controller (DC) in its local copy of Active Directory. This can happen if, after the backup was made, the object was deleted on another DC more than 180 days ago.

When a DC deletes an object it replaces the object with a tombstone object. The tombstone object is a placeholder that represents the deleted object. When replication occurs, the tombstone object is transmitted to the other DCs, which causes them to delete the AD object as well.

Tombstone objects are kept for 180 days, after which they are garbage-collected and removed.

If a DC is restored from a backup that contains an object deleted elsewhere, the object will re-appear on the restored DC. Because the tombstone object on the other DCs has been removed, the restored DC will not receive the tombstone object (via replication), and so it will never be notified of the deletion. The deleted object will “linger” in the restored local copy of Active Directory.

How to Remove Lingering Objects

Windows Server 2003 and 2008 have the ability to manually remove lingering objects using the console utility console utility REPADMIN.EXE. Use the command:

REPADMIN.EXE /removelingeringobjects .