# Perform a Rolling Update on a DaemonSet

Perform a Rolling Update on a DaemonSetThis page shows how to perform a rolling update on a DaemonSet.Before you beginYou need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:iximiuz LabsKillercodaKodeKloudPlay with KubernetesDaemonSet Update StrategyDaemonSet has two update strategy types:OnDelete: With OnDelete update strategy, after you update a DaemonSet template, new DaemonSet pods will only be created when you manually delete old DaemonSet pods. This is the same behavior of DaemonSet in Kubernetes version 1.5 or before.RollingUpdate: This is the default update strategy.With RollingUpdate update strategy, after you update a DaemonSet template, old DaemonSet pods will be killed, and new DaemonSet pods will be created automatically, in a controlled fashion. At most one pod of the DaemonSet will be running on each node during the whole update process.Performing a Rolling UpdateTo enable the rolling update feature of a DaemonSet, you must set its .spec.updateStrategy.type to RollingUpdate.You may want to set .spec.updateStrategy.rollingUpdate.maxUnavailable (default to 1), .spec.minReadySeconds (default to 0) and .spec.updateStrategy.rollingUpdate.maxSurge (defaults to 0) as well.Creating a DaemonSet with RollingUpdate update strategyThis YAML file specifies a DaemonSet with an update strategy as 'RollingUpdate'controllers/fluentd-daemonset.yaml apiVersion: apps/v1 kind: DaemonSet metadata: name: fluentd-elasticsearch namespace: kube-system labels: k8s-app: fluentd-logging spec: selector: matchLabels: name: fluentd-elasticsearch updateStrategy: type: RollingUpdate rollingUpdate: maxUnavailable: 1 template: metadata: labels: name: fluentd-elasticsearch spec: tolerations: # these tolerations are to have the daemonset runnable on control plane nodes # 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:v5.0.1 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 After verifying the update strategy of the DaemonSet manifest, create the DaemonSet:kubectl create -f https://k8s.io/examples/controllers/fluentd-daemonset.yaml Alternatively, use kubectl apply to create the same DaemonSet if you plan to update the DaemonSet with kubectl apply.kubectl apply -f https://k8s.io/examples/controllers/fluentd-daemonset.yaml Checking DaemonSet RollingUpdate update strategyCheck the update strategy of your DaemonSet, and make sure it's set to RollingUpdate:kubectl get ds/fluentd-elasticsearch -o go-template='{{.spec.updateStrategy.type}}{{"\n"}}' -n kube-system If you haven't created the DaemonSet in the system, check your DaemonSet manifest with the following command instead:kubectl apply -f https://k8s.io/examples/controllers/fluentd-daemonset.yaml --dry-run=client -o go-template='{{.spec.updateStrategy.type}}{{"\n"}}' The output from both commands should be:RollingUpdate If the output isn't RollingUpdate, go back and modify the DaemonSet object or manifest accordingly.Updating a DaemonSet templateAny updates to a RollingUpdate DaemonSet .spec.template will trigger a rolling update. Let's update the DaemonSet by applying a new YAML file. This can be done with several different kubectl commands.controllers/fluentd-daemonset-update.yaml apiVersion: apps/v1 kind: DaemonSet metadata: name: fluentd-elasticsearch namespace: kube-system labels: k8s-app: fluentd-logging spec: selector: matchLabels: name: fluentd-elasticsearch updateStrategy: type: RollingUpdate rollingUpdate: maxUnavailable: 1 template: metadata: labels: name: fluentd-elasticsearch spec: tolerations: # these tolerations are to have the daemonset runnable on control plane nodes # 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:v5.0.1 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 Declarative commandsIf you update DaemonSets using configuration files, use kubectl apply:kubectl apply -f https://k8s.io/examples/controllers/fluentd-daemonset-update.yaml Imperative commandsIf you update DaemonSets using imperative commands, use kubectl edit :kubectl edit ds/fluentd-elasticsearch -n kube-system Updating only the container imageIf you only need to update the container image in the DaemonSet template, i.e. .spec.template.spec.containers[*].image, use kubectl set image:kubectl set image ds/fluentd-elasticsearch fluentd-elasticsearch=quay.io/fluentd_elasticsearch/fluentd:v2.6.0 -n kube-system Watching the rolling update statusFinally, watch the rollout status of the latest DaemonSet rolling update:kubectl rollout status ds/fluentd-elasticsearch -n kube-system When the rollout is complete, the output is similar to this:daemonset "fluentd-elasticsearch" successfully rolled out TroubleshootingDaemonSet rolling update is stuckSometimes, a DaemonSet rolling update may be stuck. Here are some possible causes:Some nodes run out of resourcesThe rollout is stuck because new DaemonSet pods can't be scheduled on at least one node. This is possible when the node is running out of resources.When this happens, find the nodes that don't have the DaemonSet pods scheduled on by comparing the output of kubectl get nodes and the output of:kubectl get pods -l name=fluentd-elasticsearch -o wide -n kube-system Once you've found those nodes, delete some non-DaemonSet pods from the node to make room for new DaemonSet pods.Note:This will cause service disruption when deleted pods are not controlled by any controllers or pods are not replicated. This does not respect PodDisruptionBudget either.Broken rolloutIf the recent DaemonSet template update is broken, for example, the container is crash looping, or the container image doesn't exist (often due to a typo), DaemonSet rollout won't progress.To fix this, update the DaemonSet template again. New rollout won't be blocked by previous unhealthy rollouts.Clock skewIf .spec.minReadySeconds is specified in the DaemonSet, clock skew between master and nodes will make DaemonSet unable to detect the right rollout progress.Clean upDelete DaemonSet from a namespace :kubectl delete ds fluentd-elasticsearch -n kube-system What's nextSee Performing a rollback on a DaemonSetSee Creating a DaemonSet to adopt existing DaemonSet pods