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Amazon EKS Troubleshooting

This chapter covers some common errors that you may see while using Amazon EKS and how to work around them.

Insufficient Capacity

If you receive the following error while attempting to create an Amazon EKS cluster, then one of the Availability Zones you specified does not have sufficient capacity to support a cluster.

Cannot create cluster 'example-cluster' because us-east-1d, the targeted availability zone, does not currently have sufficient capacity to support the cluster. Retry and choose from these availability zones: us-east-1a, us-east-1b, us-east-1c

Retry creating your cluster with subnets in your cluster VPC that are hosted in the Availability Zones returned by this error message.

aws-iam-authenticator Not Found

If you receive the error "aws-iam-authenticator": executable file not found in $PATH, then your kubectl is not configured for Amazon EKS. For more information, see Installing aws-iam-authenticator.

Worker Nodes Fail to Join Cluster

There are two common reasons that prevent worker nodes from joining the cluster:

  • The aws-auth-cm.yaml file does not have the correct IAM role ARN for your worker nodes. Ensure that the worker node IAM role ARN (not the instance profile ARN) is specified in your aws-auth-cm.yaml file. For more information, see Launching Amazon EKS Linux Worker Nodes.

  • The ClusterName in your worker node AWS CloudFormation template does not exactly match the name of the cluster you want your worker nodes to join. Passing an incorrect value to this field results in an incorrect configuration of the worker node's /var/lib/kubelet/kubeconfig file, and the nodes will not join the cluster.

Unauthorized or Access Denied (kubectl)

If you receive one of the following errors while running kubectl commands, then your kubectl is not configured properly for Amazon EKS or the IAM user or role credentials that you are using do not map to a Kubernetes RBAC user with sufficient permissions in your Amazon EKS cluster.

  • could not get token: AccessDenied: Access denied

  • error: You must be logged in to the server (Unauthorized)

  • error: the server doesn't have a resource type "svc"

This could be because the cluster was created with one set of AWS credentials (from an IAM user or role), and kubectl is using a different set of credentials.

When an Amazon EKS cluster is created, the IAM entity (user or role) that creates the cluster is added to the Kubernetes RBAC authorization table as the administrator (with system:master permissions). Initially, only that IAM user can make calls to the Kubernetes API server using kubectl. For more information, see Managing Users or IAM Roles for your Cluster. Also, the AWS IAM Authenticator for Kubernetes uses the AWS SDK for Go to authenticate against your Amazon EKS cluster. If you use the console to create the cluster, you must ensure that the same IAM user credentials are in the AWS SDK credential chain when you are running kubectl commands on your cluster.

If you install and configure the AWS CLI, you can configure the IAM credentials for your user. If the AWS CLI is configured properly for your user, then the AWS IAM Authenticator for Kubernetes can find those credentials as well. For more information, see Configuring the AWS CLI in the AWS Command Line Interface User Guide.

If you assumed a role to create the Amazon EKS cluster, you must ensure that kubectl is configured to assume the same role. Use the following command to update your kubeconfig file to use an IAM role. For more information, see Create a kubeconfig for Amazon EKS. 

aws --region region eks update-kubeconfig --name cluster_name --role-arn arn:aws:iam::aws_account_id:role/role_name

To map an IAM user to a Kubernetes RBAC user, see Managing Users or IAM Roles for your Cluster.

hostname doesn't match

Your system's Python version must be 2.7.9 or greater. Otherwise, you receive hostname doesn't match errors with AWS CLI calls to Amazon EKS. For more information, see What are "hostname doesn't match" errors? in the Python Requests FAQ.

getsockopt: no route to host

Docker runs in the 172.17.0.0/16 CIDR range in Amazon EKS clusters. We recommend that your cluster's VPC subnets do not overlap this range. Otherwise, you will receive the following error: 

Error: : error upgrading connection: error dialing backend: dial tcp 172.17.nn.nn:10250: getsockopt: no route to host

CNI Log Collection Tool

The Amazon VPC CNI plugin for Kubernetes has its own troubleshooting script (which is available on worker nodes at /opt/cni/bin/aws-cni-support.sh) that you can use to collect diagnostic logs for support cases and general troubleshooting.

The script collects the following diagnostic information:

  • L-IPAMD introspection data

  • Metrics

  • Kubelet introspection data

  • ifconfig output

  • ip rule show output

  • iptables-save output

  • iptables -nvL output

  • iptables -nvL -t nat output

  • A dump of the CNI configuration

  • Kubelet logs

  • Stored /var/log/messages

  • Worker node's route table information (via ip route)

  • The sysctls output of /proc/sys/net/ipv4/conf/{all,default,eth0}/rp_filter

Use the following command to run the script on your worker node:

sudo bash /opt/cni/bin/aws-cni-support.sh

Note

If the script is not present at that location, then the CNI container failed to run. You can manually download and run the script with the following command: 

curl https://raw.githubusercontent.com/aws/amazon-vpc-cni-k8s/master/scripts/aws-cni-support.sh | sudo bash

The diagnostic information is collected and stored at /var/log/aws-routed-eni/aws-cni-support.tar.gz.