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This chapter is from the book

Administering OUs

As you know, it is more efficient to organize your disk files in folders than to keep them in the root directory of a disk. Similarly, you are usually better off when you store Active Directory users, groups, and other objects in "folders" called OUs (organizational units). These OUs form an OU tree (also referred to as a domain structure) inside your domain. Figure 3.5 illustrates this.

03fig05.gifFigure 3.5 OUs inside a domain form an OU tree.

In Figure 3.5, the uppermost circle (the root of the tree) is not an OU but rather the domain object that represents the domain (the triangle). We could drop the domain object out of the image, but it's more natural to have the tree as a whole. Also, in many ways the domain object behaves like an OU, so you can think of it as part of the tree.

Features of OUs

Besides providing a logical structure through the OU tree, OUs offer the following benefits.

  • An OU is a Group Policy target, so you can assign a different Group Policy to each OU.

  • If you want to delegate administration of some Active Directory objects, the most convenient way to do so is to put them in one OU and delegate administration of that OU. You could delegate administration of even single users and other objects, but the outcome would be difficult to manage. If you stick to only per-OU permissions, it is easier for you to track what you are doing.

  • Using per-OU permissions, you can control object visibility—that is, which objects and object properties various users may see.

Unfortunately, even though you can assign permissions for OUs, you cannot assign permissions to OUs. In other words, you cannot define that all users in a certain OU get access to a certain folder or other resource. This will probably result in extra work for you, because you need to create a security group and put all the users in this group to give them access.

In NDS you can give permissions to OUs, so there is no need to create a group to correspond to each OU.

In Active Directory, OUs are not related to partitioning the directory database. They are purely logical units inside a domain. The domain in turn is the partition unit.

If there are several domains in your forest, each has a totally independent OU tree. The OU tree of an upper domain does not "continue" to a tree in a lower domain. However, if you have a Windows 2000 workstation and look at the tree by selecting My Network Places, Entire Network, Directory, you will see the child domains as siblings of the first-level OUs, as Figure 3.6 illustrates. Windows XP or Windows Server 2003 doesn't show Directory in My Network Places.

03fig06.gifFigure 3.6 The Sales domain is a child of the Sanao domain. If you look at the tree via My Network Places of Windows 2000, you will see Sales as a sibling of the first-level OUs of Sanao.

Although it is not supported by Microsoft, you can enable the OU browsing of Windows 2000 also in Windows XP. Just copy the file DSFolder.dll from Windows 2000 to the System32 folder of Windows XP and register it with the command regsvr32 dsfolder.dll.

In NDS, all OUs form one big tree.

OUs are created primarily for administrators' use—end users don't usually see OUs. For example, when an end user performs a search operation for other people in Active Directory (by clicking the Start button and selecting Search), the user doesn't see the found users' OUs at all, and he couldn't even if he wanted to. For example, if there is a Jack Brown in OU Sales and another Jack Brown in OU Production, the person doing the search cannot tell the difference between them from the search dialog box. This is also true if a user is searching for a certain printer.

On the other hand, if the user has a Windows 2000 workstation and selects My Network Places, Entire Network, Directory, he will be able to browse the OU tree and see which user or printer is in which OU.

It is a matter of opinion whether hiding the OU tree from users is a good or bad thing.

Managing OUs

Managing OUs includes the following tasks:

  • Creating OUs

  • Setting OU properties

  • Moving, renaming, and deleting OUs

  • Setting Group Policy, checking the Resultant Set of Policy (RSoP), assigning a COM+ partition set, assigning permissions, and delegating administrative tasks

In this chapter, we focus on the first three items in the list. The last item is discussed in later chapters as follows: Group Policy and RSoP, see Chapter 7; permissions and delegating, see Chapter 4; and COM+ partition sets, see Windows Server 2003 Help and Support Center.

As you read on, we encourage you to try these management tasks in your domain. You cannot do any irreversible harm to your domain.

Creating OUs

Creating an OU is as easy as creating a disk folder. Just follow these steps:

  1. Launch the Users and Computers snap-in.

  2. Right-click the parent OU you want (or the domain object) and choose New, Organizational Unit.

  3. Type in the name you want and press Enter.

Unfortunately, the Insert key doesn't do the trick here as it does with the NwAdmin software for NDS.

The maximum number of characters in an OU's name is 64, which is usually more than enough. After all, it is best to use short (but descriptive) names. The OU name is a Unicode character string, so at least in theory you could have some Gurmukhi characters in an OU name. You could also put all the possible punctuation characters in an OU name, but this would make your life harder if every now and then you had to type the distinguished name of such an OU.

Setting OU Properties

After you have created an OU, you can set its properties by right-clicking the OU and choosing Properties. The dialog box in Figure 3.7 will appear.

03fig07.gifFigure 3.7 Some of the properties that you can enter for an OU include address-related information.

Table 3.6 lists the property choices. None of them affects the way Windows works. They just provide information for human beings.

Table 3.6. Properties of an OU Object


LDAP Name [*]






Text (1,024) [**]




street (Street-Address)

Text (1,024) (Each new line takes two characters.)




l (Locality-Name)

Text (128)




st (State-Or-Province-Name)

Text (128)



Zip/Postal Code


Text (40)


Country/region [***]

co (Text-Country)

Text (128)


c (Country-Name)

Text (3)






Managed By


DN [****] (You select a user or contact from a list.)


Table 3.6 shows the property LDAP names, which you will need if you use certain Resource Kit utilities or scripting, or if you set per-property permissions. One of the properties in the table is indexed, and five are part of the global catalog. Indexing makes searches faster, and the global catalog makes reading properties faster if you have multiple domains and sites.

When you set properties for an OU, if you add a user in the Managed By tab as the "manager" of an OU, that user doesn't get any permissions for the OU. This setting is purely informational. The other fields on that tab are the manager's properties, not the OU's.

Behind the scenes, the base schema lists 123 possible properties for an OU (104 in AD2000). Most of them are not used, so it doesn't matter that you can set only a few of them using the Users and Computers snap-in.

If you have Advanced Features turned on in the Users and Computers snap-in, you will see also the Security and Object tabs in the properties dialog box. The information in the former tab is discussed in Chapter 4, and the information in the latter tab is discussed in Chapter 5.

Moving, Renaming, and Deleting OUs in a Tree

You may find that your original OU tree is no longer optimal as a result of either insufficient planning or changed circumstances. If you need to rearrange your OU tree, you can easily move, rename, and delete OUs.

To move an OU inside a domain, either (a) drag it to a new location with the mouse, (b) use cut/paste with the keyboard or mouse, or (c) right-click the OU, select Move, and then choose the destination from the OU tree that opens up and click OK.

Note that not all of the OU's group policies and permissions move with it.

  • Group policies and permissions that are assigned for the object being moved move with the object.

  • Group policies and permissions that are inherited from above do not move with the object being moved. Instead, the OU will inherit new ones in its new location.

You can move several sibling OUs at once. Select them in the right-hand pane of the snap-in by using the Shift and/or Ctrl keys. Then proceed as previously described.

If you want to move an OU to another domain in your forest, you need to use another tool, such as the Support Tools command-line tool MoveTree. It is discussed further in Chapter 6.

You can rename an OU either by right-clicking the OU and selecting Rename or by selecting the OU and pressing F2. After you type the new name, press Enter.

Similarly, you delete an OU by right-clicking it and selecting Delete or by selecting the OU and pressing the Delete key. If the OU being deleted contains other objects, you are prompted to accept deleting them, too.

Planning OUs

Even though "OU" stands for "organizational unit," you don't necessarily create OUs to match the organizational units of your company. You create OUs for administrative units, physical locations, and object types (e.g., an OU for users, an OU for printers, and so on), or you can create OUs based on corporate structure.

OU trees are like folder trees on disk: There isn't just one "right" way to create them. When planning your OUs, keep in mind the following aspects of OUs:

  • OUs are purely logical entities: They are not related to physical partitions or replication.

  • OUs are for delegation of administration.

  • OUs are for Group Policy (including application publishing and assignment).

  • OUs are for controlling object visibility.

  • OUs are easy to reorganize. However, reorganizing them may confuse some users if they have learned a certain structure.

  • Each OU should have a specific need and purpose to exist.

  • There is no practical limit on how deep the OU tree can be. However, keep in mind the previous bullet about a specific purpose for each OU.

  • OUs are mainly administrative units; typically users do not see them (although Windows 2000 users can if they want).

If you have more than one domain, you might want the OU trees in all domains to be planned according to similar principles.

The aforesaid suggests that you should create OUs based on how administration is organized in your organization. The three typical scenarios are the following:

  • Geographical: If Boston has its own administrators and London has its own, you should probably create the Boston and London OUs.

  • Object type: If some people administer users and others administer printers, you should probably create the Employees and Printers OUs, for example.

  • Organization: If the Sales department has its own administrators and Production has its own, you should probably create the Sales and Production OUs.

It is also quite possible that more than one of these three divisions are used in your organization. In this case, you should create one level based on one division and another level based on another division. For example, your top-level OUs could be based on geography, and second-level OUs based on object type.

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