What is Kubernetes DaemonSet?

Question

Accepted Answer

**DaemonSet** — runs a Pod on every (or specific) Node.

```yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd
  namespace: kube-system
spec:
  selector:
    matchLabels:
      name: fluentd
  template:
    metadata:
      labels:
        name: fluentd
    spec:
      tolerations:
      - key: node-role.kubernetes.io/control-plane
        effect: NoSchedule
      - key: node.kubernetes.io/not-ready
        effect: NoExecute
      nodeSelector:
        node-type: worker
      containers:
      - name: fluentd
        image: fluent/fluentd-kubernetes-daemonset:v1.16
        resources:
          limits:
            memory: 200Mi
            cpu: 200m
          requests:
            memory: 100Mi
            cpu: 100m
        volumeMounts:
        - name: varlog
          mountPath: /var/log
          readOnly: true
        - name: containers
          mountPath: /var/lib/docker/containers
          readOnly: true
      volumes:
      - name: varlog
        hostPath:
          path: /var/log
      - name: containers
        hostPath:
          path: /var/lib/docker/containers
```

**Use cases:**
- Log collection (Fluentd, Fluent Bit).
- Monitoring agents (Prometheus Node Exporter).
- Network plugins (Calico, Cilium).
- Storage drivers.

**Update Strategy:**
- RollingUpdate: one at a time.
- OnDelete: manual trigger.

DevOps: What is Kubernetes DaemonSet?