1.3. Indirect Integration

The main advantage of the indirect integration is to manage Linux systems and policies related to those systems centrally while enabling users from Active Directory (AD) domains to transparently access Linux systems and services. There are two different approaches to the indirect integration:
Trust-based solution
The recommended approach is to leverage Identity Management (IdM) in Red Hat Enterprise Linux as the central server to control Linux systems and then establish cross-realm Kerberos trust with AD, enabling users from AD to log on to and to use single sign-on to access Linux systems and resources. This solution uses the Kerberos capability to establish trusts between different identity sources. IdM presents itself to AD as a separate forest and takes advantage of the forest-level trusts supported by AD.
In complex environments, a single IdM forest can be connected to multiple AD forests. This setup enables better separation of duties for different functions in the organization. AD administrators can focus on users and policies related to users while Linux administrators have full control over the Linux infrastructure. In such a case, the Linux realm controlled by IdM is analogous to an AD resource domain or realm but with Linux systems in it.

Note

In Windows, every domain is a Kerberos realm and a DNS domain at the same time. Every domain managed by the domain controller needs to have its own dedicated DNS zone. The same applies when IdM is trusted by AD as a forest. AD expects IdM to have its own DNS domain. For the trust setup to work, the DNS domain needs to be dedicated to the Linux environment.
Note that in trust environments, IdM enables you to use ID views to configure POSIX attributes for AD users on the IdM server. For details, see:
Synchronization-based solution
An alternative to a trust-based solution is to leverage user synchronization capability, also available in IdM or Red Hat Directory Server (RHDS), allowing user accounts (and with RHDS also group accounts) to be synchronized from AD to IdM or RHDS, but not in the opposite direction. User synchronization has certain limitations, including:
  • duplication of users
  • the need to synchronize passwords, which requires a special component on all domain controllers in an AD domain
  • to be able to capture passwords, all users must first manually change them
  • synchronization supports only a single domain
  • only one domain controller in AD can be used to synchronize data to one instance of IdM or RHDS
In some integration scenarios, the user synchronization may be the only available option, but in general, use of the synchronization approach is discouraged in favor of the cross-realm trust-based integration.