3.3. Role concept#
Univention Corporate Server (UCS) uses a role concept to assign different roles that comprise certain tasks to the systems in a domain.
3.3.1. Primary Directory Node#
A UCS system with Primary Directory Node role is the first, the primary, domain node in a domain. It is the only system with write permissions to the central domain database and performs all write requests regarding data for the domain database. Only one system in the domain can have the Primary Directory Node role.
3.3.2. Backup Directory Node#
A UCS system with the Backup Directory Node role has a complete read-only copy of the domain database, including security certificates. More than one UCS system can have the Backup Directory Node role. In case the Primary Directory Node is unavailable, recovery is impossible or needs too much time, an administrator can promote a UCS system in the role Backup Directory Node to a Primary Directory Node. The promotion cannot be reversed. For details on the promotion process, see Converting a Backup Directory Node backup to the new Primary Directory Node.
3.3.3. Replica Directory Node#
UCS systems with the Replica Directory Node role have a complete read-only copy of the domain database. Administrators cannot promote Replicate Directory Nodes to the Primary Directory Node role or any other role unlike the Backup Directory Node.
A Replica Directory Node optionally allows selective replication, a form of data synchronization that replicates only a subset of the domain database. Selective replication in UCS helps with data minimization, domain protection and permission enforcement.
For example, imagine an organization with office locations in cities like Berlin and Bremen. Each location has a Replica Directory Node as domain node. The Replica Directory Nodes only replicate domain objects like users, groups and printers that are relevant for their respective location. They don’t store objects assigned to other locations.
Replica Directory Nodes are ideally suited as dedicated systems for load intensive services with permanent read operations to the domain database because the read operations run locally instead of across the computer network.
3.3.4. Managed Node#
UCS systems with the Managed Node role don’t have any copy of the domain database. Services on Managed Nodes read domain information over the network from either the Primary Directory Node or from one of the Backup Directory Nodes.
Clients are systems in the domain’s trust context. They don’t have a special role regarding domain services as the other roles described before. In most cases they consume services offered by the domain or other systems.
UCS offers dedicated client roles for desktop systems like Ubuntu, other Linux desktops and macOS. UCS manages IP addresses and DNS entries for systems like network printers and routers with the IP client role.
For Microsoft Windows related systems, UCS offers the roles Domain Trust Account, Windows Domaincontroller and Windows Workstation / Server. For more information about the differences of these roles see UCS system roles.