K3s PodFailedToSchedule

A pod failed to schedule due to constraints or lack of resources.

Understanding K3s: A Lightweight Kubernetes Distribution

K3s is a lightweight Kubernetes distribution designed for resource-constrained environments and edge computing. It is a fully compliant Kubernetes distribution that is easy to install and operate, making it ideal for IoT and CI/CD environments. K3s is packaged as a single binary, reducing the complexity and overhead associated with traditional Kubernetes installations.

Identifying the Symptom: PodFailedToSchedule

One common issue encountered in K3s is the PodFailedToSchedule error. This error occurs when a pod cannot be scheduled onto a node. The symptom is typically observed in the pod's status, where it remains in a Pending state, and the events describe a scheduling failure.

Exploring the Issue: Why Pods Fail to Schedule

The PodFailedToSchedule error usually arises due to insufficient resources or scheduling constraints. Kubernetes uses a scheduler to place pods on nodes based on resource availability and constraints defined in the pod's specification. If the scheduler cannot find a suitable node, the pod remains unscheduled.

Common Causes

Insufficient CPU or memory resources on nodes.
Node taints and tolerations preventing scheduling.
Node selectors or affinity rules that are too restrictive.

Steps to Resolve PodFailedToSchedule

To resolve the PodFailedToSchedule issue, follow these steps:

1. Check Resource Availability

Ensure that your nodes have sufficient resources. Use the following command to check node resources:

kubectl describe nodes

Look for available CPU and memory resources. If resources are low, consider adding more nodes or resizing existing ones.

2. Review Pod Specifications

Examine the pod's resource requests and limits. Ensure they are reasonable and within the capacity of your nodes. Adjust if necessary:

kubectl describe pod <pod-name>

3. Check Node Taints and Tolerations

Nodes may have taints that prevent pods from scheduling. Verify node taints with:

kubectl describe node <node-name>

Ensure your pod has the necessary tolerations to match these taints.

4. Verify Node Selectors and Affinity Rules

Ensure that any node selectors or affinity rules in your pod specification are not overly restrictive. Adjust them as needed to allow scheduling on available nodes.

Additional Resources

For more information on troubleshooting scheduling issues in Kubernetes, refer to the official Kubernetes Scheduling Documentation. Additionally, the K3s Documentation provides insights specific to K3s environments.

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MORE ISSUES

K3s PodFailedToWatch

A pod failed to watch, possibly due to misconfiguration or resource issues.

K3s PodFailedToWrite

A pod failed to write, possibly due to misconfiguration or resource issues.

K3s PodFailedToWait

A pod failed to wait, possibly due to misconfiguration or resource issues.

K3s PodFailedToVerify

A pod failed to verify, possibly due to misconfiguration or resource issues.

K3s PodFailedToValidate

A pod failed to validate, possibly due to misconfiguration or resource issues.

K3s PodFailedToUpdate

A pod failed to update, possibly due to misconfiguration or resource issues.

K3s PodFailedToAttachVolume

A pod failed to attach a volume, possibly due to incorrect volume configuration.

K3s PodFailedToStop

A pod failed to stop, possibly due to finalizers or resource cleanup issues.

K3s PodFailedToStartContainer

A pod failed to start a container, possibly due to misconfiguration or resource issues.

K3s PodFailedToPullImage

A pod failed to pull an image, possibly due to incorrect image name or lack of access.

K3s PodFailedToSchedule

A pod failed to schedule due to constraints or lack of resources.

K3s PodFailedToMountVolume

A pod failed to mount a volume, possibly due to incorrect volume configuration.

K3s NodeNotReadyDueToDiskPressure

A node is not ready due to disk pressure, affecting pod scheduling.

K3s PodFailedToStart

A pod failed to start due to misconfiguration or resource issues.

K3s PodFailedToCreate

A pod failed to create due to misconfiguration or resource issues.

K3s PodFailedToDelete

A pod failed to delete, possibly due to finalizers or resource cleanup issues.

K3s NodeNotRegistered

A node is not registered with the cluster, affecting pod scheduling.

K3s PodSecurityContextViolation

A pod violates security context constraints, preventing it from running.

K3s PodOOMKilled

A pod was killed due to out-of-memory conditions.

K3s PodLivenessProbeFailure

A pod's liveness probe is failing, causing the pod to be restarted.

K3s PodAffinityRulesNotSatisfied

Pod affinity or anti-affinity rules are not satisfied, preventing scheduling.

K3s PodReadinessProbeFailure

A pod's readiness probe is failing, affecting service availability.

K3s PodInitContainerFailure

An init container in a pod has failed, preventing the pod from starting.

K3s Pods are not being scheduled on a node due to a taint.

A node taint is preventing pod scheduling.

K3s Ingress resources are not accessible.

Ingress resources are not accessible, possibly due to misconfiguration.

K3s Service account token has expired, affecting pod authentication.

A service account token has expired.

K3s Pod cannot pull an image due to missing or incorrect image pull secret.

A pod is unable to access the required image because the image pull secret is either missing or incorrectly configured.

K3s PodSecurityPolicyViolation

A pod violates a PodSecurityPolicy, preventing it from being scheduled.

K3s Network policies are blocking traffic, affecting pod communication.

Network policies are blocking traffic, affecting pod communication.

K3s Kubelet service is not running on a node, affecting pod management.

The kubelet service is not running on a node.

K3s Pod stuck in terminating state

A pod is stuck in terminating state, possibly due to finalizers or resource cleanup issues.

K3s NodeOutOfDisk

A node has run out of disk space, affecting pod scheduling and operation.

K3s UnauthorizedAccess

Access is denied due to incorrect credentials or permissions.

K3s API requests are timing out

Network issues or high load on the API server

K3s PersistentVolumeClaimPending

A PersistentVolumeClaim is pending due to lack of available PersistentVolumes.

K3s Network is unavailable on a node, affecting pod communication.

Network configuration issues or connectivity problems.

K3s NodeNotFound

A specified node cannot be found, possibly due to incorrect node name or deletion.

K3s FailedScheduling

A pod cannot be scheduled due to constraints or lack of resources.

K3s High memory usage observed in K3s cluster.

Excessive memory usage by pods or system components, causing resource exhaustion.

K3s NodeDiskPressure

A node is experiencing disk pressure, leading to pod eviction or scheduling issues.

K3s FailedMount

A pod cannot mount a volume, possibly due to incorrect volume configuration.

K3s Pods are unable to resolve DNS names.

CoreDNS issues causing DNS resolution failure.

K3s Pods are being evicted unexpectedly.

Pods are evicted due to resource constraints or node pressure.

K3s High CPU Usage

Excessive CPU usage by pods or system components, leading to performance degradation.

K3s PodUnschedulable

A pod cannot be scheduled due to insufficient resources or node constraints.

K3s ImagePullBackOff

K3s is unable to pull the specified container image, possibly due to incorrect image name or lack of access.

K3s Communication failures between K3s components due to expired certificates.

K3s certificates have expired, causing communication failures between components.

K3s ServiceUnavailable

A service is not reachable, possibly due to misconfigured service or network policies.

K3s NodeNotReady

The node is not in a ready state, possibly due to network issues or resource constraints.

K3s CrashLoopBackOff

A pod is repeatedly crashing due to application errors or misconfiguration.

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