Use context: kubectl config use-context k8s-c1-H
Use Namespace project-tiger for the following. Create a DaemonSet named ds-important with image httpd:2.4-alpine and labels id=ds-important and uuid=18426a0b-5f59-4e10-923f-c0e078e82462. The Pods it creates should request 10 millicore cpu and 10 mebibyte memory. The Pods of that DaemonSet should run on all nodes, also controlplanes.
Creating a DaemonSet in Kubernetes from a Deployment
DaemonSets are a critical feature in Kubernetes, allowing you to ensure that a copy of a Pod runs on every node in your cluster. However, if you’re working with a situation where you cannot directly create a DaemonSet using kubectl, you can start by creating a Deployment and then converting it into a DaemonSet. In this guide, we’ll walk through how to do just that.
Step 1: Create a Deployment
Since we aren’t able to create a DaemonSet directly, we’ll start by creating a Deployment and then modify it. First, generate a Deployment YAML file:
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kubectl -n project-tiger create deployment --image=httpd:2.4-alpine ds-important --dry-run=client -o yaml > 11.yaml |
This command will create a Deployment YAML file named 11.yaml. Now, let’s edit this file to convert the Deployment into a DaemonSet.
Step 2: Modify the YAML to Create a DaemonSet
Open the 11.yaml file in your preferred text editor (e.g., vim) and make the following changes:
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# 11.yaml apiVersion: apps/v1 kind: DaemonSet # Change from Deployment to DaemonSet metadata: name: ds-important namespace: project-tiger # Ensure this is set to the correct namespace labels: # Add these labels id: ds-important uuid: 18426a0b-5f59-4e10-923f-c0e078e82462 spec: selector: matchLabels: id: ds-important # Add these labels uuid: 18426a0b-5f59-4e10-923f-c0e078e82462 template: metadata: labels: id: ds-important # Add these labels uuid: 18426a0b-5f59-4e10-923f-c0e078e82462 spec: containers: - image: httpd:2.4-alpine name: ds-important resources: requests: # Add resource requests cpu: 10m memory: 10Mi tolerations: # Add toleration to ensure the DaemonSet runs on all nodes - effect: NoSchedule key: node-role.kubernetes.io/control-plane |
In this YAML file, we changed the kind from Deployment to DaemonSet, removed unnecessary fields like replicas and strategy, and added resource requests and tolerations to ensure the DaemonSet runs on all nodes, including control-plane nodes.
Step 3: Apply the DaemonSet Configuration
Now that the YAML file is properly configured, apply it to your Kubernetes cluster:
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kubectl apply -f 11.yaml |
After applying, verify that the DaemonSet is running on all nodes:
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kubectl -n project-tiger get ds kubectl -n project-tiger get pods -l id=ds-important -o wide |
You should see output similar to the following, confirming that the DaemonSet is running on all nodes:
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NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE ds-important 3 3 3 3 3 <none> 8s NAME READY STATUS NODE ds-important-6pvgm 1/1 Running cluster1-node1 ds-important-lh5ts 1/1 Running cluster1-controlplane1 ds-important-qhjcq 1/1 Running cluster1-node2 |
Conclusion
In this guide, we’ve demonstrated how to create a DaemonSet in Kubernetes by first generating a Deployment and then modifying it. This method is useful when direct creation of a DaemonSet is not possible via kubectl. By understanding the YAML structure and the required changes, you can easily ensure that your application runs across all nodes in your cluster.