Introduction

An LDAP directory, such as Active Directory, stores data in a hierarchy of containers and leaf nodes called the directory information tree (DIT). Leaf nodes are end points in the tree, while containers can store other containers and leaf nodes. In Active Directory, the two most common types of containers are organizational units (OUs) and container objects. The container objects are generic containers that do not have any special properties about them other than that they can contain objects. Organizational units, on the other hand, have some special properties, such as being able to be linked to a group policy. In most cases, when designing a hierarchy of objects in Active Directory, especially users and computers, you should use OUs instead of containers. There is nothing you can do with a container that you can't do with an OU, but the reverse is not true.

The Anatomy of an Organizational Unit

Organizational units can be created anywhere in a Domain naming context. The one exception is that by default OUs cannot be added as a child of a container object. See Recipe 5.10 for more on how to work around this. OUs are represented in Active Directory by organizationalUnit objects. Table 5-1 contains a list of some interesting attributes that are available on organizationalUnit objects.

Table 5-1. Attributes of organizationalUnit objects

Attribute	Description
description	Textual description of the OU.
gPLink	List of group policy objects (GPOs) that have been linked to the OU. See Recipe 5.11 for more information.
gpOptions	Contains 1 if GPO inheritance is blocked and 0 otherwise.
msDS-Approx-Immed-Subordinates	Approximate number of direct child objects in the OU. See Recipe 5.8 for more information.
managedBy	Distinguished name (DN) of user or group that is in charge of managing the OU.
ou	Relative distinguished name of the OU.
modifyTimestamp	Timestamp of when the OU was last modified.
createTimestamp	Timestamp of when the OU was created.