Terraforming the Cluster

Terraform is a configuration management program which
enables creation of cloud-based resources using specifications
written in a domain-specific language (DSL) called the
Hashicorp Configuration Language (HCL).

Installing Terraform

Terraform can be downloaded from the
Terraform website.

Mac install

brew install terraform

Windows Install

choco install terraform

Linux Install

wget https://releases.hashicorp.com/terraform/0.12.26/terraform_0.12.26_linux_amd64.zip
unzip terraform_0.12.26_linux_amd64.zipterraform_0.12.26_linux_amd64.zip
sudo mv terraform /usr/local/bin
sudo chmod +x /usr/local/bin/terraform

Additionally, when setting up Terraform in bash, an
alias can be set to shorten the Terraform command.

alias tf=/usr/bin/tf

Setting up Cloud Access

Terraform configures access to different clouds using plugins known
as providers. For the purpose of this tutorial, the
kubernetes
and
kubectl.

The Kubernetes provider is built into Terraform.

Installing kubectl

The kubectl provider is a 3rd party Terraform provider which uses kubectl to provision YAML charts for Kubernetes.

The kubectl provider needs to be manually installed
through an external plugin.

$ mkdir -p ~/.terraform.d/plugins && \
    curl -Ls https://api.github.com/repos/gavinbunney/terraform-provider-kubectl/releases/latest \
    | jq -r ".assets[] | select(.browser_download_url | contains(\"$(uname -s | tr A-Z a-z)\")) | select(.browser_download_url | contains(\"amd64\")) | .browser_download_url" \
    | xargs -n 1 curl -Lo ~/.terraform.d/plugins/terraform-provider-kubectl && \
    chmod +x ~/.terraform.d/plugins/terraform-provider-kubectl

⚠ Unfortunately there were not Windows installation instructions on the kubectl provider
page. The above instructions should work for Windows Subsytem for Linux (WSL), Mac, and
Linux.

Provisioning Resources on Kubernetes

With the installation of Terraform and the Kubernetes providers complete, Terraform can be
configured to provision resources on the Kubernetes cluster. Create a file called terraform.tf.

provider "kubernetes" {}

provider "kubectl" {}

Both the Kubernetes provider and the kubectl provider provide custom options which can be found in
the documentation:

• Kubernetes provider - https://www.terraform.io/docs/providers/kubernetes/index.html
• kubectl provider - https://gavinbunney.github.io/terraform-provider-kubectl/docs/provider.html

The Terraform configuration can be initialized with the terraform init command.

Terraform specifications

The kubectl provider offers YAML-based creation of Kubernetes resources using the kubectl plugin.

An example of a namespace is demonstrated below:

resource "kubectl_manifest" "mf_demo_ns" {
    yaml_body = <<YAML
        apiVersion: v1
        kind: Namespace
        metadata:
            name: demo
    YAML
}

The Kubernetes provider enables creation of Kubernetes resources which are standard to the
Kubernetes Manifest DSL. Terraform provides
detailed documentation
which correspond directly to Kubernetes constructs. The detailed configuration can be found on the
Data Sources and Resources sections of the documentation.