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Step-by-step instructions for performing operations with Kubernetes.

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Performing a Rolling Update on a DaemonSet

This page shows how to perform a rolling update on a DaemonSet.

Before you begin

DaemonSet Update Strategy

DaemonSet has two update strategy types :

Limitations

Caveat: Updating DaemonSet created from Kubernetes version 1.5 or before

If you try to rolling update a DaemonSet that was created from Kubernetes version 1.5 or before, a rollout will be triggered when you first change the DaemonSet update strategy to RollingUpdate, even when DaemonSet template isn’t modified. All existing DaemonSet pods will be restarted.

To avoid this restart, first find the DaemonSet’s current .spec.templateGeneration:

kubectl get ds/<daemonset-name> -o go-template='{{.spec.templateGeneration}}{{"\n"}}'

The output should be a number N. If the output shows <no value>, N = 0.

Then, simply label the existing DaemonSet pods with pod-template-generation=<N> before changing DaemonSet .spec.updateStrategy to RollingUpdate:

# Replace N with DaemonSet `.spec.templateGeneration`
# Only run this on pods created from current DaemonSet template
kubectl label pods -l <daemonset-selector-key>=<daemonset-selector-value> pod-template-generation=<N>

This tells the DaemonSet that the labeled DaemonSet pods are created from current DaemonSet template. Therefore, you should only run this command to existing DaemonSet pods that are generated from current DaemonSet template.

Note that you only need to do this when you first change the update strategy of a DaemonSet created from Kubernetes version 1.5 or before to RollingUpdate, but don’t want to update its template and start a new rollout yet.

Setting DaemonSet update strategy for rolling update

To 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) and .spec.minReadySeconds (default to 0) as well.

Step 1: Checking DaemonSet RollingUpdate update strategy

First, check the update strategy of your DaemonSet, and make sure it’s set to RollingUpdate:

kubectl get ds/<daemonset-name> -o go-template='{{.spec.updateStrategy.type}}{{"\n"}}'

If you haven’t created the DaemonSet in the system, check your DaemonSet manifest with the following command instead:

kubectl create -f ds.yaml --dry-run -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.

Step 2: Creating a DaemonSet with RollingUpdate update strategy

If you have already created the DaemonSet, you may skip this step and jump to step 3.

After verifying the update strategy of the DaemonSet manifest, create the DaemonSet:

kubectl create -f ds.yaml

Alternatively, use kubectl apply to create the same DaemonSet if you plan to update the DaemonSet with kubectl apply.

kubectl apply -f ds.yaml

Step 3: Updating a DaemonSet template

Any updates to a RollingUpdate DaemonSet .spec.template will trigger a rolling update. This can be done with several different kubectl commands.

Declarative commands

If you update DaemonSets using configuration files, use kubectl apply:

kubectl apply -f ds-v2.yaml

Imperative commands

If you update DaemonSets using imperative commands, use kubectl edit or kubectl patch:

kubectl edit ds/<daemonset-name>
kubectl patch ds/<daemonset-name> -p=<strategic-merge-patch>
Updating only the container image

If you just 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/<daemonset-name> <container-name>=<container-new-image>

Step 4: Watching the rolling update status

Finally, watch the rollout status of the latest DaemonSet rolling update:

kubectl rollout status ds/<daemonset-name> 

When the rollout is complete, the output is similar to this:

daemon set "<daemonset-name>" successfully rolled out

Troubleshooting

DaemonSet rolling update is stuck

Sometimes, a DaemonSet rolling update may be stuck. Here are some possible causes:

Some nodes run out of resources

The 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 <daemonset-selector-key>=<daemonset-selector-value> -o wide 

Once you’ve found those nodes, delete some non-DaemonSet pods from the node to make room for new DaemonSet pods. Note that this will cause service disruption if the deleted pods are not controlled by any controllers, or if the pods aren’t replicated. This doesn’t respect PodDisruptionBudget either.

Broken rollout

If 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, just update the DaemonSet template again. New rollout won’t be blocked by previous unhealthy rollouts.

Clock skew

If .spec.minReadySeconds is specified in the DaemonSet, clock skew between master and nodes will make DaemonSet unable to detect the right rollout progress.

What’s next

TODO: Link to “Task: Creating a DaemonSet to adopt existing DaemonSet pods”

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