A Crash Course in Active Directory



Uses DNS for name resolution

WINS and NetBios aren’t needed unless a legacy app requires it

AD’s Tree is called the ‘Directory Information Tree’ (DIT)

It is based on the ‘Extensible Storage Engine’ (ESE)

AD Consists of two types of objects. Containers and non-containers (or leaf nodes)

All objects have a ‘Globally Unique Identifier’ (GUID)

Hierarchical paths in AD are known as ‘ADsPaths’

ADsPaths are normally referred to using LDAP standards

 Starts with a 'programmatic identifier' (progID)  followed by ://  separate each part with a comma  prefix each part with dc= (dc stands for domain name component)    prl.pbb.local becomes  LDAP://dc=pbb,dc=pbb,dc=local

A distinguished name (DN) is used to reference an object in a DIT

A relative distinguished name (RDN) is used to reference an object within its parent container

 To reference Alice's object in prl_biz ou within the prl ou it would look like this.  LDAP://cn=albin,ou=prl_biz,ou=prl,dc=pbb,dc=pbb,dc=local

The available DN’s are as follows

 CN = Common Name  L  = Locality  ST = Street of Province Name  O  = Organization Name  OU = Organization Unit  C  = County  STREET = Street address  DC = Domain Component  UID = User ID

domains and domain trees

A domain controller (DC) can be authoritative for one and only one domain.

Containers (the object type) may contain other container objects as well as leaf nodes.

An OU is the other type of container and can have group policies applied to it, and a container (the object) can not.

Each forest has a child container called ‘Configuration’ which has a child container called ‘Schema’

Global Catalog (GC)

Used to perform forest wide searches

Accessed via LDAP on port 3268

Uses progID of GC://

The GC is read-only and can not be directly updated

Objects available in the GC are members of the PAS (Partial Attributes Set)

To add/remove attributes use the AD Schema snap-in for mmc

Flexible Single Master of Operations (FSMO – pronounced fizmo)

Certain actions in the forest/domain will only be done by the FSMO regardless of how many other DC’s you have.

 Schema Master (forest-wide)    Only machine allowed to make schema changes.  Changes made on other DCs will be refered to the FSMO    Domain Naming Master (forest-wide)    PDC Emulator (domain-wide)    PW synching and PDC legacy compatibility.  Browser Master    RID Master (domain-wide)    Relative ID Master, All security principals have a Security Identifier (SID).    Infrastructure Master (domain-wide)    Maintains cross-domain object references (phantom references).  User is in domainA but a member of a group in domain B

 NTDSUTIL:   howto: [1]  download: support pack [2]  Allows transfer of FSMO roles to other DCs.  If the FSMO server dies you can ungracefully force the role to another dc -- known as 'seizing' the role. [3]


3 scopes…

 Domain Local: membership available only within domain.  May contain other groups (admin group)

 Domain Global: membership available only within domain.  Used to define roles (enterprise admin, backup admin, exchange admins, sql admins, ect.)

 Universal: Forest Wide

2 types…

 distribution: generally used as messaging lists for email and im (exchange distro lists)

 security: sid is passed to as auth token

The type of a group may be converted at any time.

Naming Contexts (NC) and Application Partitions

Breaks up replication of DCs. can be based on political, geographic or bw related things.

Consists of 3 predefined naming contexts, each represents a different aspect of AD data.

 Configuration NC: (forest) holds data pertaining to LDAP, Exchange, subnets

 Schema NC: (forest) defines types of data AD can store

 Domain NC: (domain) domain specific, users, groups, computers, ect.

 Application Partitions: User defined NCs.  Can not contain security principals

To retrieve a list of NCs you query the RootDSE entry.

 LDAP util  how to: [4]  download: support tools [5]   LDAP util can be used to view the RootDSE entry.  Connection -> Connection -> enter name of DC

… incomplete


The schema is located under the configuration container. It is the blueprint for datastorage in ad. each object has a corresponding class. IE user class, user object type.

 Active Directory Service Interfaces (ADSIEdit)  how to: [6]  download: support tools [7]   Can be viewed using and AD viewer such as ADSIEdit (MMC snap-in) or LDP

Schema is made of two types of ad objects…


… Very Incomplete


Note: details regarding cross-domain replication omitted.

Connection Objects define what DCs replicate with each other and how often. Generally managed by the DC

Knowledge Consistency Checker (KCC) is what generates the connection objects.

 RepAdmin  how to: [8]   Command line tool for admining replication
ReplMon  how to: [9]  Graphical util for managing and monitoring replication

Each DC maintains its own separate ‘Update Sequence Number’ (USN). It is a 64bit value assigned to each update transication. Each update increments the USN value. Like the serial number in DNS.

Each DC maintains its highest combined USN for all NCs in the highestCommittedUSN value of the RootDSE. The values are always different from DC to DC for a given replication.

If time is off by 5minutes or more on a DC it will not be able to replicate.

Originating Update (write)  The point of origin for an update (on which DC was this update made)
Replicated Update (write)  A change that did not originate on the DC in question.

Each DC has a GUID called the DSA GUID. It is used to uniquely identify a DC and is the objectGUID of the NTDS settings object for the DC in the configuration container.

The High-WaterMark Vector (HWMV) is a table maintained independently by each DC. Keeps info on where a DC last left off when replicating the NC with a specific partner.

The up-to-dateness vector (UTDV) is a table maintained independently by each DC. It is used for replication dampening to reduce traffic and endless replication.

An example of how an object is modified during replication…

1.  A user is created on serverA.  2.  The object (user) is replicated to serverB.  3.  The object is subsequently modified on serverB.  4.  The new changes are replicated back to serverA.
1.  Creation of the object on ServerA    1. values are set to defaults defined for user creation    2. users USN is set to 1000 (the USN of this transaction)    3. version number is set to 1.    4. timestamp is set to the time of creation    5. originating-server GUID is set to the GUID of the server    6. originating-server USN is set to 1000 (USN of this transaction)
2.  Replication of the object to serverB    serverB adds a copy of the object as a replicated write.  USN 2500 is assigned to the object.  This value is written to the USNCreated and USNChanged attributes of the object.
3.  Password changed for user on serverB.    1. Password value is set    2. passwords USN is set to 3777 (USN for this transaction)    3. users version number is set to 2.    4. timestamp is updated    5. originating-server GUID is set to the GUID of serverB    6. originating-server USN is set to 3777 (USN of this transaction)
4.  Password change replication to serverA    serverA generates a transaction USN of 1333.  USNChanged is set to 1333.  Originating-server GUID is set to that of serverB

… Incomplete (missing conflict resolution section)

AD and DNS

DC Locator

Resource Records used to AD

Delegation Options

… incomplete (duh)


A profile is created on each computer a user logs into. It is %systemDrive%\Documents and Settings\%userName%

It creates various data files including NTUSER.DAT. This file contains the user portion of the registry. This includes the screen saver, wallpaper, myDocuments location, etc.

Settings specific to the computer in question are also applied to the user via the AllUsers\NTUSER.DAT on the given machine.

You use the ADUC (Active Directory Users and Computers) tool to set the roaming profile info for a given user.

To have the profile deleted from the local machine upon logout set the following key on the computer (computer and teaching labs!)…


With a server based default user profile you can add icons to desktop, bookmarks, ect. It should exist under the NETLOGON share.

Group Policy

Group Policies are referred to GPOs or group policy objects. they contain a large amount of configuration info that is applied to all users automatically.

 Group Policy Management Console (GPMC)  howto: [10]  Allows for editing, viewing resultant set of policies (RSOP) and runing reports.

Three states a policy item can exist in are enabled, disabled or un-configured. unconfigured is the default for everything.

The structure of the templates in the editor looks like…

User Configuration    Software Settings    Windows Settings    Administrative Templates    Computer Configuration    Software Settings    Windows Settings    Administrative Templates

These are generated from the Administrative Template (ADM) files in the system volume.

By default workstations and member servers refresh GPOs every 90 minutes and DCs every 5.

On non DCs 1 to 30 minutes (randomly generated) will be added to the refresh time to avoid everyone checking in at once.

GPOs allow admin to remote deploy applications to users OR computers. MSI is the only way this works.

MSIs can be modified for the environment. This process is known as creating a ‘transform’.

You can set an MSI to auto-install when someone attempts to open a file with an extension that an MSI app can read.

If an install is assigned to the user portion of the GPO it will install when the user logs into a machine and uninstall upon log off. If its installed to the computer it is available to any user who logs into it.

MS Windows Installer  howto: [11]   Used to generate MSI files
Install Shield  site: [12]  The best tools in the installer maker.  3rd party
Installer Design Studio (scriptlogic)  site: [13]  The one scriptlogic makes.  Looks very easy to use and is fairly inexpensive.
Group Policy Settings Reference (document) : [14]
Group Policy Homepage : [15]
MSN docs for Group Policy : [16]

Backup, Recovery and Maintenance

Backup up AD

Restoring a DC

Restoring AD

FSMO recovery

DIT Maintenance

… Incomplete (duh)

Exchange Integration

… incomplete (duh)


Common admin tasks: [17]

Remote Administration: [18]

All information gleaned from…

Active Directory 3d Edition, O’Reilly Publishing By: Joe Richards, Robbie Allen & Alistair G. Lowe-Norris

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