Kubernetes DaemonSets
Kubernetes Daemonset can be used to run replicas of a pod on specific or all nodes.
- https://kubernetes.io/docs/concepts/workloads/controllers/daemonset/
- https://kubernetes.io/docs/concepts/workloads/controllers/replicaset/#daemonset
Typical uses of a DaemonSet are:
- Running a cluster storage daemon on every node
- Running a logs collection daemon on every node
- Running a node monitoring daemon on every node
Official example
https://kubernetes.io/docs/concepts/workloads/controllers/daemonset/
apiVersion: apps/v1 kind: DaemonSet metadata: name: fluentd-elasticsearch namespace: kube-system labels: k8s-app: fluentd-logging spec: selector: matchLabels: name: fluentd-elasticsearch template: metadata: labels: name: fluentd-elasticsearch spec: tolerations: # these tolerations are to have the daemonset runnable on control plane node # remove them if your control plane nodes should not run pods - key: node-role.kubernetes.io/control-plane
operator: Exists
effect: NoSchedule
- key: node-role.kubernetes.io/master
operator: Exists
effect: NoSchedule
containers:
- name: fluentd-elasticsearch
image: quay.io/fluentd_elasticsearch/fluentd:v2.5.2
resources:
limits:
memory: 200Mi
requests:
cpu: 100m
memory: 200Mi
volumeMounts:
- name: varlog
mountPath: /var/log
- name: varlibdockercontainers
mountPath: /var/lib/docker/containers
readOnly: true
terminationGracePeriodSeconds: 30
volumes:
- name: varlog
hostPath:
path: /var/log
- name: varlibdockercontainers
hostPath:
path: /var/lib/docker/containers
Activities
- CKA v1.18: Understand the role of DaemonSets
- Stop daemonset:
kubectl patch daemonset <name-of-daemon-set> -p '{"spec": {"template": {"spec": {"nodeSelector": {"non-existing": "true"}}}}}'
Related terms
kubectl api-resourceskind: DaemonSetkubectl get daemonset, kubectl get daemonset -Akubectl rollout daemonset- StatefulSet
See also
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