Fixing Kubernetes PVC "Pending" Status: A Comprehensive Troubleshooting Guide

When embedding persistent storage in your Kubernetes applications, encountering the "Pending" status on Persistent Volume Claims (PVCs) can be a common but problematic issue. This status indicates that Kubernetes has not yet been able to provision the required storage for your PVC. Understanding the root cause and how to solve it is essential for ensuring your storage needs are met and your applications run smoothly. Here’s a comprehensive guide on how to troubleshoot and resolve PVCs stuck in the "Pending" status.

Step 1: Describe the PVC

The first step is to describe the PVC to understand why it is in the "Pending" state:

kubectl describe pvc <pvc-name>

This command provides detailed information, including events that might indicate why the PVC is not getting bound.

Step 2: Check for Available Persistent Volumes (PVs)

PVCs need to bind to PVs that satisfy their requirements. List the existing PVs and verify their statuses:

kubectl get pv

Ensure there are PVs in the "Available" state that match the storage class, size, and access modes specified in the PVC.

Step 3: Verify Storage Classes

Mismatched or incorrect storage classes often lead to PVCs being stuck in the "Pending" state. Ensure that your PVC is requesting the correct storage class:

        apiVersion: v1
        kind: PersistentVolumeClaim
        metadata:
          name: mypvc
        spec:
          accessModes:
            - ReadWriteOnce
          storageClassName: standard
          resources:
            requests:
              storage: 5Gi
        

Verify that the specified storage class is available in your cluster:

kubectl get storageclass

Step 4: Check Storage Provisioner Logs

Storage provisioners, be it cloud-based or on-premises solutions, manage the dynamic creation of PVs. If there are issues with the storage provisioner, the PVC might remain in the "Pending" state. Consult the provisioner's logs for more detailed insights:

kubectl logs -n <provisioner-namespace> <provisioner-pod-name>

Look for errors or warnings that might indicate why the dynamic provisioning is failing.

Step 5: Node Affinity and Taints

Sometimes PVCs might not bind due to node affinity rules or taints/tolerations. Ensure there are nodes that match the affinity rules and can host the PVs. Additionally, confirm that the nodes are not tainted in a way that prevents them from accepting the PVs:

kubectl describe nodes

Step 6: Permissions and Quotas

Ensure that your Kubernetes cluster has sufficient permissions and quotas to provision the requested storage:

kubectl get resourcequotas

Check if there are any limitations imposed that might prevent creating new PVs or PVCs.

Step 7: Manually Create and Bind PVs

If dynamic provisioning fails, you can manually create and bind a PV to your PVC. First, create a PV manifest:

        apiVersion: v1
        kind: PersistentVolume
        metadata:
          name: mypv
        spec:
          capacity:
            storage: 5Gi
          accessModes:
            - ReadWriteOnce
          persistentVolumeReclaimPolicy: Retain
          storageClassName: standard
          hostPath:
            path: "/mnt/data"
        

Apply the PV and then re-check the PVC status:

kubectl apply -f <persistent-volume-manifest.yaml>

Conclusion

Persistent Volume Claims stuck in the "Pending" status can halt the deployment of critical applications. By systematically describing the PVC, verifying available PVs and storage classes, checking provisioner logs, examining node affinity and taints, ensuring permissions and quotas, and finally, manually creating PVs if necessary, you can resolve this issue effectively. A well-maintained Kubernetes storage setup ensures that your applications have the persistent storage they need to run smoothly.