What is a DaemonSet used for?

The DaemonSet controller creates a pod for each node that matches its node selector and tolerations. When a node joins, a pod is added; when it leaves, the pod is cleaned up. There is no replica count because the node set determines the count.

• Use nodeSelector or affinity to limit which nodes get the pod
• Add tolerations for control-plane taints if the agent must run there
• A DaemonSet pod often needs hostPath or hostNetwork access
• Resource requests matter because the agent consumes capacity on every node
• Rolling updates replace pods node by node according to maxUnavailable

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: node-exporter
spec:
  selector:
    matchLabels:
      app: node-exporter
  template:
    metadata:
      labels:
        app: node-exporter
    spec:
      tolerations:
        - key: node-role.kubernetes.io/control-plane
          operator: Exists
          effect: NoSchedule
      containers:
        - name: exporter
          image: registry.example.com/node-exporter:1.8.1
          resources:
            requests:
              cpu: 50m
              memory: 64Mi

Because DaemonSets touch every node, a bad rollout has cluster-wide blast radius. Stage changes on a small node pool, keep resource requests tight and verify that the agent tolerates node pressure rather than competing with application pods.