Migrating from Windows Server 2003/2008 to Windows Server 2008 R2 : Multiple Domain Consolidation Migration (part 1)

Figure 1. CompanyXYZ forest.

However, this can be disruptive to the users and applications if not handled carefully. Migrating to a new domain and forest results in changes to the security identifiers, which can impact access. It can also result in password changes, making it difficult for users. However, there are tools and techniques, which are explored in this section, to mitigate the impact to the users and applications.

The introduction of Windows Server 2008 coincided with improvements in the Active Directory Migration Tool, a fully functional domain migration utility. ADMT version 3.1 allows Active Directory users, computers, and groups to be consolidated, collapsed, or restructured to fit the design needs of an organization. In regard to Windows Server 2003/2008 migrations, ADMT v3.1 provides for the flexibility to restructure existing domain environments into new Windows Server 2008 R2 Active Directory environments, keeping security settings, user passwords, and other settings.

Understanding ADMT v3.1 Functionality

ADMT is an effective way to migrate users, groups, and computers from one domain to another. It is robust enough to migrate security permissions and Exchange mailbox domain settings. ADMT is composed of the following components and functionality:

• ADMT migration wizards— ADMT includes a series of wizards, each designed to migrate specific components. You can use different wizards to migrate users, groups, computers, service accounts, and trusts.

• Low client impact— ADMT automatically installs a service on source clients negating the need to manually install client software for the migration. In addition, after the migration is complete, these services are automatically uninstalled.

• SID History and security migrated— Users can continue to maintain network access to file shares, applications, and other secured network services through migration of the SID History attributes to the new domain. This preserves the extensive security structure of the source domain.

ADMT v3.1 installs very easily but requires a thorough knowledge of the various wizards to be used properly. In addition, best-practice processes should be used when migrating from one domain to another.

The migration example in the following sections describes the most common use of the Active Directory Migration Tool: an interforest migration of domain users, groups, and computers into another domain. This procedure is by no means exclusive, and many other migration techniques can be used to achieve proper results. Subsequently, matching the capabilities of ADMT with the migration needs of an organization is important.

Using ADMT in a Lab Environment

You can develop the most effective lab by creating new domain controllers in the source and target domains and then physically segregating them into a lab network, where they cannot contact the production domain environment. The Operations Master (OM) roles for each domain can then be seized for each domain using the NTDSUTIL utility, which effectively creates exact replicas of all user, group, and computer accounts that can be tested with the ADMT.

ADMT v3.1 Installation Procedure

Install the ADMT component on a Windows Server 2008 domain controller in the target domain, where the accounts will be migrated to. To install, follow these steps:

ADMT Domain Migration Prerequisites

As previously mentioned, the most important prerequisite for migration with ADMT is lab verification. Testing as many aspects of a migration as possible can help to establish the procedures required and identify potential problems before they occur in the production environment.

That said, several technical prerequisites must be met before the ADMT can function properly. These are as follows:

• Create two-way trusts between source and target domains— The source and target domains must each be able to communicate with each other and share security credentials. Consequently, it is important to establish trusts between the two domains before running the ADMT.

• Assign proper permissions on source domain and source domain workstations— The account that will run the ADMT in the target domain must be added into the Builtin\Administrators group in the source domain. In addition, each workstation must include this user as a member of the local Administrators group for the computer migration services to be able to function properly. Domain group changes can be easily accomplished, but a large workstation group change must be scripted, or manually accomplished, prior to migration.

• Create the target OU structure— The destination for user accounts from the source domain must be designated at several points during the ADMT migration process. Establishing an organizational unit (OU) for the source domain accounts can help to simplify and logically organize the new objects. These objects can be moved to other OUs after the migration and this OU collapsed, if you want.