Within the IdM domain, information is shared among servers and replicas by copying that information, reliably and predictably, between data masters (servers and replicas). This process is replication.
A similar process can be used to share data between the IdM domain and a Microsoft Active Directory domain. This is synchronization.
Synchronization is the process of copying user data back and forth between Active Directory and Identity Management.
Synchronization is defined in an agreement between an IdM server and an Active Directory domain controller. The sync agreement defines all of the information required to identify sync-able user entries (like the subtree to synchronize and requisite object classes in the user entries) as well as defining how account attributes are handled. The sync agreements are created with default values which can be tweaked to meet the needs of a specific domain. When two servers are involved in synchronization, they are called peers.
Synchronization is most commonly bi-directional. Information is sent back and forth between the IdM domain and the Windows domain in a process that is very similar to how IdM servers and replicas share information among themselves. It is possible to configure synchronization to only sync one way. That is uni-directional synchronization.
To prevent the risk of data conflicts, synchronization is configured between one Identity Management server and one Active Directory domain controller. The Identity Management server propagates changes back to the IdM domain, while the domain controller propagates changes back to the Windows domain.
There are some key features to IdM synchronization:
A synchronization operation runs every five minutes.
Synchronization can only be configured with one Active Directory domain. Multiple domains are not supported.
Synchronization can only be configured with one Active Directory domain controller.
Only user information is synchronized.
Both user attributes and passwords can be synchronized.
While modifications are bi-directional (going both from Active Directory to IdM and from IdM to Active Directory), creating or adding accounts are only uni-directional, from Active Directory to Identity Management. New accounts created in Active Directory are synchronized over to IdM automatically. However, user accounts created in IdM must also be created in Active Directory before they will be synchronized.
Account lock information is synchronized by default, so a user account which is disabled in one domain is disabled in the other.
Password synchronization changes take effect immediately.
When Active Directory users are synchronized over to IdM, certain attributes (including Kerberos and POSIX attributes) will have IPA attributes are automatically added to the user entries. These attributes are used by IdM within its domain. They are not synchronized back over the corresponding Active Directory user entry.
Some of the data in synchronization can be modified as part of the synchronization process. For examples, certain attributes can be automatically added to Active Directory user accounts when they are synced over to the IdM domain. These attribute changes are defined as part of the synchronization agreement and are described in Section 15.5.3, “Changing the Behavior for Syncing User Account Attributes”