In this lesson, you will learn how to systematically diagnose and resolve common failures when Kubernetes fails to attach or mount persistent storage to your pods.
When a pod remains in a ContainerCreating or Pending state, it is often because the Container Storage Interface (CSI) driver is struggling to provide the requested volume. Storage issues usually stem from three areas: misconfigured StorageClasses, insufficient permissions for the CSI driver, or connectivity issues between the node and the storage backend.
Diagnosing with Pod Events
The first step is always to inspect the pod’s status and events. Run kubectl describe pod <pod-name> and look at the Events section at the bottom. Common error messages include FailedMount or FailedAttachVolume. These messages often reveal the underlying culprit:
- Permission Denied: The CSI controller service account lacks the IAM or RBAC permissions to communicate with your cloud provider’s storage API.
- Node Stage/Publish Error: The driver can reach the storage, but the node cannot "see" the disk or file system. This usually points to network issues or missing drivers on the node.
Inspecting Controller Logs
If the event logs are vague, the CSI controller logs are your next destination. CSI drivers run as pods in the kube-system (or a dedicated) namespace. You can view them using:
kubectl logs -n kube-system -l app=csi-driver-controller-name
Look for error or failed keywords during the timestamp that matches your pod deployment. If the controller reports "Access Denied," you likely need to review your RBAC configuration or the secret credentials provided to the driver.
Permission and Configuration Check
If the storage is provisioned but fails to mount, verify that the VolumeAttachment object exists:
kubectl get volumeattachment
If the status shows an error, the control plane is failing to map the storage to the node. Ensure your StorageClass uses the correct provisioner name and that the reclaimPolicy matches your requirements. Sometimes, simply deleting a stuck PersistentVolumeClaim and recreating it—after verifying the driver is healthy—can resolve transient binding errors.
Key Takeaway: When storage mounting fails, always start with kubectl describe pod to find the specific error stage, then pivot to the CSI controller pod logs to identify if the fault lies in API permissions or node-level network connectivity.