Using custom AMI ID for EKS Nodegroup

Question

We have tried to build launch templates using a custom AMI we have subscribed to from the AMI catalog. When doing this, we have been able to launch instances using Auto-Scaling Group features with that AMI but doesn't create nodes within our EKS cluster. Is there another method to create Node Groups using custom AMI's? When trying to create Node Groups manually in the cluster, the creation runs to failure with the message "Instances failed to join the Kubernetes cluster".

Answer

Using a custom AMI for an EKS node group requires a few considerations to ensure that the instances can properly join and function within the Kubernetes cluster managed by Amazon EKS. Here are some steps and checks you can perform to troubleshoot the issue:

Ensure that the custom AMI is compatible with EKS requirements (e.g., pre-installed packages, configurations). Compare its configuration with that of the [Amazon EKS Optimized AMI](https://docs.aws.amazon.com/eks/latest/userguide/eks-optimized-ami.html).
Use the [EKS bootstrap script](https://docs.aws.amazon.com/eks/latest/userguide/bootstrap.html) (/etc/eks/bootstrap.sh) in your launch template in the user data section.
Verify IAM role for node group has necessary EKS permissions.
Check VPC, subnets, and security groups for proper configuration allowing communication with the EKS control plane and internet.
Ensure instances are tagged correctly (e.g., kubernetes.io/cluster/ = owned).
Inspect CloudWatch Logs for bootstrap process errors.
Check the Auto Scaling Group's Activity History for instance launch errors.
Confirm the EKS Cluster Role has eks:DescribeCluster permission.

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Using custom AMI ID for EKS Nodegroup

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