Which of the following is NOT part of firewalld's configuration?

Firewalld uses a concept known as zones to manage different levels of trust for network connections, which helps in defining rules for how a given network can interact with the system. Each zone corresponds to a specific level of security that can include various services and interfaces.

In this configuration, a service represents a set of rules that can be allowed or denied based on the zone in which the service is defined. An interface is a network interface that can be associated with a specific zone, which allows fine control over which interfaces have which rules applied based on the network's trust level.

While a "chain" is a term found in iptables—another Linux firewall management tool—it is not a part of firewalld's configuration. Firewalld abstracts many of the details involved in managing firewall rules by using zones, services, and interfaces rather than chains, which is more of a lower-level concept used in iptables.

Thus, recognizing that chains do not apply to firewalld helps clarify its configuration and management strategies, focusing instead on the accessible and user-friendly abstractions that firewalld provides.