A DaemonSet ensures that a copy of a Pod runs on each node (or a selected subset of nodes), which matches option A and makes it correct. DaemonSets are ideal for node-level agents that should exist everywhere, such as log shippers, monitoring agents, CNI components, storage daemons, and security scanners.
DaemonSets differ from Deployments/ReplicaSets because their goal is not "N replicas anywhere," but "one replica per node" (subject to node selection). When nodes are added to the cluster, the DaemonSet controller automatically schedules the DaemonSet Pod onto the new nodes. When nodes are removed, the Pods associated with those nodes are cleaned up. You can restrict placement using node selectors, affinity rules, or tolerations so that only certain nodes run the DaemonSet (for example, only Linux nodes, only GPU nodes, or only nodes with a dedicated label).
Option B sounds like a ReplicaSet/Deployment behavior (stable set of replicas), not a DaemonSet. Option C describes CronJobs (scheduled, recurring run-to-completion workloads). Option D describes StatefulSets, which provide stable identity, ordering, and uniqueness guarantees for stateful replicas.
Operationally, DaemonSets matter because they often run critical cluster services. During maintenance and upgrades, DaemonSet update strategy determines how those node agents roll out across the fleet. Since DaemonSets can tolerate taints (like master/control-plane node taints), they can also be used to ensure essential agents run across all nodes, including special pools. Thus, the correct definition is A.
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