As described in previous articles, group policy in Active Directory allows us a great deal of flexibility in terms of how users and their Windows 2000 computing environment is controlled and managed. Things that can be done with group policy include software distribution, updating settings such as Internet Explorer’s proxy server settings, locking people out of Control Panel, and so forth. It is worth investigating the hundreds of settings that can be configured in group policy, but unnecessary to remember all (or even most) of them. However, be sure to at least familiarize yourself with the different possible settings and why they exist.
The main reason for the existence of group policy is to be able to control the user environment and make changes with the least amount of administrative effort. For example, I could remove the My Network Places icon from certain user desktops by setting up a group policy object applied to an OU. When users whose account exists within that OU would log on, the icon would not be available for them, regardless of what system they logged on to within the Active Directory forest (unless a conflicting policy had also been configured at another level, as we’ll discuss in a moment).
Although the idea behind group policy settings is pretty straightforward, it can be confusing to configure them correctly, since settings can be made at many different levels. Group policy objects (GPOs) can be applied at the following levels:
OU (and sub-OU)
The order listed above is also the order in which policy settings are applied. What that means is that policy settings at all levels merge with one another (with exceptions when Block Inheritance and No Override are used, to be discussed later). As such, if a local group policy says that I lose the Run command, site group policy says I lose access to Control Panel, domain group policy says my desktop wallpaper is the corporate logo, and the OU policy redirects my My Documents folder, then when I log on all of those things will happen. However, in the event that a conflict exists (for example the site policy takes away Run, while the OU policy says it should be available), then the lower-level policy settings take precedence.
Local GPOs are stored on the local system, and only one can exist on a Windows 2000 machine. All other GPOs – those applied to sites, domains, and OUs – are stored in Active Directory. Actually, a GPO is made up of two parts. The group policy container is stored in the AD database (this contains most settings), while larger ‘extras’ such as logon scripts are stored in the group policy template, which is stored within the Sysvol folder on a domain controller. The path to where policy templates are stored is %systemroot%\SYSVOL\sysvol\domain_name\Policies, where the folder name for the template is the globally unique identifier (GUID) of the GPO.
Group policy objects can be created by using the Group Policy MMC snap-in, but are usually created from within Active Directory Users and Computers. Remember that GPOs can only be configured and applied to the local system, sites, domains, and OUs. As such, you cannot be applied to the default built-in containers, such as Users or Computers. To create a new group policy object, right-click the appropriate container in AD Users and Computers and access the Group Policy tab. To create a new policy, click New, and give the policy a name.
You can also add an existing policy. This is useful, especially if you wanted to link the same GPO to many OUs that required identical settings. After you have named the OU, you need to click on Edit to actually configure the policy settings.
Note that settings fall into two major areas, Computer Configuration and User Configuration. Settings in the top portion apply to Computer Accounts and settings in the bottom apply to User Accounts. As such, if your computer account were in an OU called Desktops, the computer configuration settings would be applied according to the GPO settings from that OU. By the same token, if your user account were in the Sales OU, user configuration settings would be applied from that OU. If either part of the OU is not being configured in a given GPO, you should disable that portion, which will speed up group policy processing. This is done by clicking the Properties button on the Group Policy tab.
Note that multiple GPOs may exist linked to the same container. In this situation, it is possible that conflicting settings exist in the policies. When multiple GPOs exist at the same level, the policies are applied from bottom to top. That is, policies at the bottom of the list are applied before those above. The settings applied later always take precedence over those applied earlier. In the example above, User Policy 3 would be applied first, followed by User Policy 2, followed by User Policy. As such, if a site policy and domain policy also existed, the order of application would be:
User Policy 3
User Policy 2
Note that if any policies were applied to sub-OUs that existed within the Company Users OU, these would be applied after those listed above.