73 lines
2.5 KiB
Markdown
73 lines
2.5 KiB
Markdown
---
|
|
title: Building a Basic DaemonSet
|
|
content_type: task
|
|
weight: 5
|
|
---
|
|
<!-- overview -->
|
|
|
|
This page demonstrates how to build a basic {{< glossary_tooltip text="DaemonSet" term_id="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.
|
|
|
|
## {{% heading "prerequisites" %}}
|
|
|
|
{{< include "task-tutorial-prereqs.md" >}}
|
|
|
|
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.
|
|
|
|
{{% code_sample file="application/basic-daemonset.yaml" %}}
|
|
|
|
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.
|
|
|
|
## {{% heading "cleanup" %}}
|
|
|
|
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/).
|
|
|
|
## {{% heading "whatsnext" %}}
|
|
|
|
* 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/)
|