Building a Basic DaemonSet [page]deterministic
This page demonstrates how to build a basic [DaemonSet](#gloss:daemonset) that runs a Pod on every node in a Kubernetes cluster. It covers a simple use case of mounting a file from the host, logging its contents using an [init container](/docs/concepts/workloads/pods/init-containers/), and utilizing a pause container.
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A Kubernetes cluster with at least two nodes (one control plane node and one worker node) to demonstrate the behavior of DaemonSets.
## Define the DaemonSet
In this task, a basic DaemonSet is created which ensures that the copy of a Pod is scheduled on every node. The Pod will use an init container to read and log the contents of `/etc/machine-id` from the host, while the main container will be a `pause` container, which keeps the Pod running.
1. Create a DaemonSet based on the (YAML) manifest:
```shell kubectl apply -f https://k8s.io/examples/application/basic-daemonset.yaml ```
1. Once applied, you can verify that the DaemonSet is running a Pod on every node in the cluster:
```shell kubectl get pods -o wide ```
The output will list one Pod per node, similar to:
``` NAME READY STATUS RESTARTS AGE IP NODE example-daemonset-xxxxx 1/1 Running 0 5m x.x.x.x node-1 example-daemonset-yyyyy 1/1 Running 0 5m x.x.x.x node-2 ```
1. You can inspect the contents of the logged `/etc/machine-id` file by checking the log directory mounted from the host:
```shell kubectl exec <pod-name> -- cat /var/log/machine-id.log ```
Where `<pod-name>` is the name of one of your Pods.
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To delete the DaemonSet, run this command:
```shell kubectl delete --cascade=foreground --ignore-not-found --now daemonsets/example-daemonset ```
This simple DaemonSet example introduces key components like init containers and host path volumes, which can be expanded upon for more advanced use cases. For more details refer to [DaemonSet](/docs/concepts/workloads/controllers/daemonset/).
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* See [Performing a rolling update on a DaemonSet](/docs/tasks/manage-daemon/update-daemon-set/) * See [Creating a DaemonSet to adopt existing DaemonSet pods](/docs/concepts/workloads/controllers/daemonset/)