Introduction

The Amazon Elastic Block Store (EBS) Container Storage Interface (CSI) driver is an essential tool for managing persistent storage within Amazon Elastic Kubernetes Service (EKS). It enables Kubernetes workloads to easily interact with Amazon EBS volumes for storing and accessing data. However, configuring and using the EBS CSI driver often involves several moving parts, and misconfigurations can lead to a variety of issues. This article explores common issues with the EBS CSI driver in EKS and offers guidance on troubleshooting and resolving them.

1. IAM Role Misconfiguration (Insufficient Permissions)

Problem:

The most prevalent issue arises from the IAM roles assigned to the EKS node group (worker nodes). If these IAM roles lack the correct permissions, the EBS CSI driver won't be able to interact with Amazon EC2 and EBS resources.

Symptoms:

• EBS volumes fail to be created, attached, or deleted.

• Errors such as "AccessDeniedException" or "PermissionDenied" are shown in the logs.

• Pods attempting to mount EBS volumes get stuck in a Pending state.

Solution:

Ensure the IAM role for the worker nodes has the necessary permissions. These include actions such as:

• ec2:DescribeVolumes

• ec2:CreateVolume

• ec2:AttachVolume

• ec2:DeleteVolume

A sample IAM policy can be used to provide these permissions. Verify the permissions using Kubernetes events and logs to ensure proper interaction between the EBS CSI driver and AWS resources.

2. EBS CSI Driver Version Mismatch

Problem:

The version of the EBS CSI driver may not be compatible with the version of EKS you're running, leading to issues in volume creation, attachment, or mounting.

Symptoms:

• Kubernetes events show errors related to the CSI driver.

• EBS volume provisioning or mounting fails.

• The EBS CSI controller pod crashes or fails to start.

Solution:

Ensure you are using a version of the EBS CSI driver that is compatible with your EKS version. Follow the official AWS documentation for instructions on upgrading or downgrading the driver version.

3. Node Group Role Missing AmazonEKSWorkerNodePolicy

Problem:

The AmazonEKSWorkerNodePolicy IAM policy is not attached to the IAM role of the node group, leading to issues with node communication with the EKS control plane.

Symptoms:

• Worker nodes fail to register with the EKS cluster.

• Error messages indicating that nodes cannot authenticate with the EKS API.

Solution:

Ensure the node IAM role includes the AmazonEKSWorkerNodePolicy. This policy provides the necessary permissions for worker nodes to communicate with the EKS control plane and pull container images from Amazon ECR.

4. EBS CSI Driver Controller Pod Fails to Start

Problem:

The EBS CSI controller pod, responsible for managing the lifecycle of EBS volumes, may fail to start or crash if there are permission issues or misconfigurations in the driver.

Symptoms:

• The controller pod enters a CrashLoopBackOff state.

• Errors such as Failed to create volume or related CSI driver errors appear in the logs.

Solution:

Check the logs of the EBS CSI driver controller pod to identify the specific issues. Often, misconfigured IAM roles or missing policies can prevent the controller from functioning. Ensure the IAM permissions are correctly set up and that the driver’s configuration is correct.

5. Volume Attachment Failure

Problem:

The EBS volume fails to attach to the node or pod due to incorrect IAM permissions, or other misconfigurations in the cluster.

Symptoms:

• Kubernetes events indicate VolumeAttachment errors.

• Pods fail to start, remaining in a Pending state.

• Error messages such as AttachVolume error: AccessDeniedException appear in logs.

Solution:

Verify that the IAM role attached to the worker nodes has the permissions necessary to attach volumes, including ec2:AttachVolume and ec2:DescribeInstances. Additionally, check the node's availability zone and ensure it matches the availability zone of the EBS volume.

6. Inconsistent EBS Volume Availability Zone

Problem:

EBS volumes are created in an availability zone (AZ) different from the EKS worker nodes, causing attachment failures.

Symptoms:

• Kubernetes events show errors such as Failed to provision volume.

• EBS volume cannot be attached to the worker node due to a mismatch in AZs.

Solution:

Make sure that the EBS volume is created in the same availability zone as the worker nodes. When provisioning volumes dynamically with the EBS CSI driver, the driver automatically provisions the volume in the correct AZ, but this needs to be verified if you are manually managing EBS volumes.

7. IAM Role Assumption Issues

Problem:

Misconfigurations in role assumption or trust relationships can prevent the EBS CSI driver from assuming the required IAM roles.

Symptoms:

• Logs show issues related to "role not assumed".

• EBS volumes fail to be managed or attached.

Solution:

Ensure the IAM role used by the EBS CSI driver has the correct trust relationship configured to allow it to be assumed by the Kubernetes service account. Double-check that the service account has been granted the correct permissions to interact with EBS resources.

8. Node Group Scaling Issues

Problem:

When scaling an EKS node group, newly added nodes may not have the appropriate IAM permissions immediately, causing issues when provisioning or attaching volumes.

Symptoms:

• Newly added nodes fail to mount or access EBS volumes.

• Node group scaling events do not function as expected.

Solution:

Ensure that the IAM roles and policies are applied to all worker nodes, including newly added nodes, and that the nodes have the appropriate IAM permissions for EBS volume interactions.

9. EBS Volume Resource Limits

Problem:

AWS imposes limits on the number of volumes that can be attached to an EC2 instance or the throughput of EBS volumes. Exceeding these limits can cause provisioning or attachment failures.

Symptoms:

• EBS volumes cannot be attached to nodes because the attachment limit has been exceeded.

• Kubernetes events show VolumeAttachment failures related to resource limits.

Solution:

Review the limits for your EC2 instance type and ensure that the number of volumes attached to the instance does not exceed the limit. If the limit is reached, consider adjusting your EC2 instance type or scaling your infrastructure.

10. Incorrect Volume Provisioning via StorageClass

Problem:

Misconfiguration of the StorageClass used for dynamic provisioning of EBS volumes can lead to issues with volume creation and attachment.

Symptoms:

• Pods fail to start because EBS volumes are not being provisioned.

• Errors related to StorageClass configuration appear in Kubernetes events.

Solution:

Verify the StorageClass configuration used for provisioning EBS volumes. Ensure the provisioner is set to ebs.csi.aws.com and check that all necessary parameters (e.g., fsType, volumeBindingMode) are correctly specified. The StorageClass must match the type of volumes you want to create and attach.

Conclusion

The EBS CSI driver is a powerful tool for managing persistent storage in Amazon EKS. However, misconfigurations and lack of correct IAM permissions can lead to numerous issues, from volume creation failures to pod startup issues. By ensuring that IAM roles are properly configured, maintaining compatibility between the EBS CSI driver and EKS versions, and correctly setting up StorageClass and volume parameters, you can avoid these common pitfalls and maintain a smooth, scalable Kubernetes infrastructure with persistent storage.