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README.md
env.sh
iam.tf
outputs.tf
provider.tf.sample
route53.tf
s3.tf
terraform.tfvars.sample
variables.tf

README.md

bootstrap

This repo contains the code for creating the AWS prerequisites for a k8s cluster on AWS via terraform, and helper code and instructions for creating an k8s cluster on AWS via terraform.

Background

Currently, kops documentation for creating a Kubernetes cluster via kops on AWS has a number of AWS prerequisites that must be in place before we can run kops. The documentation enumerates these prerequisites in the Setup your environment section. At the time of this commit, kops needs a kops IAM user with the proper permissions, an s3 bucket in which kops can store state, and the proper DNS configuration. Note, Kops supports a number of different DNS configuration options. We use Scenario 1b., where we own and manage a root domain in Route53, and want Kubernetes to use a subdomain of the root domain for its DNS records.

kops documentation provides procedural shell commands using the aws cli. This project accomplishes the same goals as those iterative commands, but using terraform. Terraform is a powerful tool for infrastructure as code, and offers considerable advantages over procedural shell commands.

As a final reminder, this Terraform configuration does not create a Kubernetes cluster. It only ensures the necessary AWS infrastructure for kops exists. Kops is responsible for creating/managing our AWS cluster. For more information on using Kops to create a cluster on AWS, see my blog post on creating a Kubernetes cluster on AWS using Kops.

Instructions

Prerequisites

Before beginning this tutorial, ensure the following are true:

  1. Terraform is installed on your machine. See download instructions if it is not.
  2. Running aws iam get-user returns a user. That user either has, or belongs to a group that has, the following policies: AmazonEC2FullAccess, IAMFullAccess, AmazonS3FullAccess, and AmazonRoute53FullAccess.
  3. You have an S3 bucket (i.e. USERNAME-terraform) in which terraform can store its state files.
  4. You own and manage a root domain (i.e. mattjmcnaughton.com) via Route53. You should see a hosted zone for your root domain in Route53.

One-time operations

While aspects of the AWS configuration are generic (i.e. everyone will use an iam user named kops), some are specific to each user. Although these variables are not secrets, I thought it would be confusing to check them into source control.

Instead, we define two separate *.sample files which illustrate the variables you need to provide, without providing values.

The first, provider.tf.sample, configures where Terraform will store its state files. Run mv provider.tf.sample provider.tf and then replace "YOUR_BUCKET_FOR_STORING_TERRAFORM_STATE" with the s3 bucket we assumed you had in step 3 of the prerequisites.

The second, terraform.tfvars.sample, defines the configurable aspects of the AWS infrastructure Kops needs in order to work successfully. You need to define three separate variables:

  • existing_base_route53_zone_name is the existing root domain that you currently manage via Route53. For me, this value is mattjmcnaughton.com..
  • k8s_route53_zone_name is the new subdomain in which kops will create all of our Kubernetes clusters DNS records. For me, this value is k8s.mattjmcnaughton.com..
  • kops_state_store_s3_bucket_name is the name of the S3 bucket in which kops will store its state. For me, this value is USERNAME-kops-state-store.

After copying and updating the template files, run terraform init.

Create/update AWS prereqs

You are now ready to create the necessary infrastructure for Kops to succeed. First, run terraform plan to see what entities terraform will create. Since you have never run terraform apply, terraform will need to create all the infrastructure you declared. terraform plan only shows what operations terraform would take if you ran terraform apply. It doesn't actually run any of them.

To actually create the infrastructure, we need to run terraform apply. The first time you run this command, terraform will create a number of new resources.

Since terraform is declarative, you can run terraform plan at any point to see if there are any differences between what your terraform configuration files declare and what actually exists in s3. If there is, and you want to apply the changes in the terraform configuration files, you can run terraform apply again.

Should you want to delete the AWS infrastructure Kops needs, you can run terraform destroy.

Use kops

Before running kops, we must ensure a given set of environment variables have the correct value. We define these variables in env.sh, so running source env.sh ensures your current shell is ready to run kops commands. As an example:

# Load necessary environment variables.
source env.sh

# Create cluster configuration.
kops create cluster --name=$NAME --state=$KOPS_STATE_STORE --zones=$AZ --ssh-public-key PATH_TO_PUBLIC_KEY

I will go into greater detail on actually using kops in my blog post on creating your own Kubernetes cluster using kops.