This assumes you have setup Terraform as described in Amazon Web Services (AWS) - Getting Started with Terraform.

A Node Group contains one or more modes, which is often an EC2 Instance.

Let's say you have the following files on your Terraform server.

├── required_providers.tf
├── elastic_kubernetes_service (directory)
│   ├── iam.tf
│   ├── node_groups.tf
│   ├── provider.tf

required_providers.tf will almost always have this.

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
    }
  }
}

Let's say provider.tf has the following. In this example, the "default" profile in /home/username/.aws/config and /home/username/.aws/credentials is being used. This assumes you have setup Terraform as described in Amazon Web Services (AWS) - Getting Started with Terraform.

provider "aws" {
  alias   = "default"
  profile = "default"
  region  = "default"
}

And iam.tf could have the following.

resource "aws_iam_role" "node_group_role" {
  name               = "node_group_role"
  assume_role_policy = data.aws_iam_policy_document.eks_node_group_assume_role_policy.json

  tags = {
    Name = "node_group_role"
  }
}


data "aws_iam_policy_document" "eks_node_group_assume_role_policy" {
  statement {
    effect  = "Allow"
    actions = ["sts:AssumeRole"]

    principals {
      type        = "Service"
      identifiers = ["ec2.amazonaws.com"]
    }
  }
}

And node_groups.tf could have the following.

resource "aws_eks_node_group" "node_group" {
  cluster_name    = "my-cluster"
  node_group_name = "my-node-group"
  node_role_arn   = aws_iam_role.node_group_role.arn
  subnet_ids      = ["subnet-111222333", "subnet-222333444"]

  capacity_type  = "ON_DEMAND"
  instance_types = ["t3.medium"]

  scaling_config {
    desired_size = 2
    max_size     = 3
    min_size     = 1
  }

  tags = {
    environment = "staging"
  }
}

The terraform plan command can be used to see what Terraform will try to do.

terraform plan

The terraform apply command can be used to create or update EKS Node Group.

terraform apply -auto-approve