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DaemonSets

Where the Deployment is like a Swiss Army Knife, usable for a broad variety of workloads and deployment strategies, the DaemonSet is like a tin opener: Built for a very specific use-case, i.e. running exactly one pod per node.

This can be useful for system utilities like log collectors, monitoring agents, or storage daemons that need to run on every node in the cluster.

In fact, we already got a DaemonSet running in our cluster:

kubectl get daemonsets,pods -n kube-system -l app=kindnet -o wide # (1)!

  1. -n kube-system tells kubectl to look for DaemonSets and Pods in the kube-system namespace.

    -l app=kindnet tells kubectl to only show objects which are labeled with app=kindnet.

    -o wide tells kubectl to show us more information in the output.

NAME                     DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR            AGE   CONTAINERS    IMAGES                                          SELECTOR
daemonset.apps/kindnet   3         3         3       3            3           kubernetes.io/os=linux   71m   kindnet-cni   docker.io/kindest/kindnetd:v20230511-dc714da8   app=kindnet

NAME                READY   STATUS    RESTARTS   AGE   IP           NODE                             NOMINATED NODE   READINESS GATES
pod/kindnet-n2xxq   1/1     Running   0          71m   172.18.0.2   workshop-cluster-worker2         <none>           <none>
pod/kindnet-nvkd2   1/1     Running   0          71m   172.18.0.4   workshop-cluster-worker          <none>           <none>
pod/kindnet-qdnvk   1/1     Running   0          71m   172.18.0.3   workshop-cluster-control-plane   <none>           <none>

The kindnet DaemonSet is a networking daemon that is responsible for networking in our cluster. It's a core component of KinD, and needs to run on every node to provide connectivity between our pods, and nodes.

Therefore, it's a perfect example for a DaemonSet and when they come in handy!

Last update: September 21, 2023
Created: September 15, 2023