K3s is a lightweight Kubernetes distribution designed for resource-constrained environments and edge computing. It simplifies the deployment and management of Kubernetes clusters by reducing the complexity and overhead associated with traditional Kubernetes installations. K3s is particularly popular for IoT and CI/CD environments due to its minimal resource requirements and ease of use.
When working with K3s, you might encounter a situation where a pod is in a Pending state with the PodUnschedulable condition. This symptom indicates that the Kubernetes scheduler is unable to place the pod on any available node in the cluster. This can be frustrating as it prevents the application from running as expected.
Pending state indefinitely.0/1 nodes are available: 1 Insufficient cpu.The PodUnschedulable issue arises when the Kubernetes scheduler cannot find a suitable node that meets the resource requests and constraints specified by the pod. This can happen due to:
Each pod can specify resource requests and limits for CPU and memory. The scheduler uses these requests to determine if a node has enough available resources to accommodate the pod. If no node meets these requirements, the pod remains unschedulable.
To resolve the PodUnschedulable issue, follow these steps:
Ensure that the resource requests and limits specified in your pod's configuration are reasonable and within the capacity of your nodes. You can view the current requests and limits using:
kubectl describe pod <pod-name>
Adjust the requests and limits if necessary.
Check the available resources on your nodes to ensure they can accommodate the pod's requirements. Use the following command to view node resources:
kubectl describe nodes
Consider adding more nodes or upgrading existing nodes if resources are insufficient.
Ensure that your pods have the necessary tolerations to be scheduled on nodes with taints. You can view node taints using:
kubectl describe node <node-name>
Modify your pod configuration to include appropriate tolerations if needed.
Check if your pod has any node selectors or affinity rules that might be too restrictive. Review and adjust these settings in your pod specification to allow for more flexible scheduling.
For more information on managing resources and scheduling in Kubernetes, refer to the following resources:
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