Truly cloud-agnostic Terraform samples

The pitch

We hear a lot about Terraform being a Cloud-agnostic tool but in the real-world, even though it can manage the major (and other) Cloud providers, it is almost impossible to deploy a full stack from one Cloud provider to another without rewriting Terraform files.

This lead to the Cloud-agnostic architecture myth.

Let's try to undebunk this myth.

Supported Cloud providers

Currently following Cloud providers are supported:

• AWS
• Hetzner
• Scaleway

Usage

Explicitly disable all providers (AWS provider is not concerned):

export HCLOUD_TOKEN=disabled
export SCALEWAY_ORGANIZATION=disabled
export SCALEWAY_TOKEN=disabled

This is a limitation of Terraform not allowing to have a count attribute in providers definition (see for instance hashicorp/terraform#19932).

AWS

1. with a given IAM user, create an access key ID and a secret access key and export them as AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables respectively (these are the default environment variable names used by the AWS Terraform provider):

export AWS_ACCESS_KEY_ID=<REDACTED>
export AWS_SECRET_ACCESS_KEY=<REDACTED>

Grant this IAM user the roles for EC2.

2. create an SSH key pair:

# generate the SSH key pair
ssh-keygen -t rsa -b 4096 -C "terraform-aws" -q -N "" -f ~/.ssh/aws

3. initialize Terraform variables:

cp terraform.tfvars.aws terraform.tfvars

This sample configuration will:

• use the previously created SSH private key
• create 2 nodes of type t2.micro with Ubuntu 18.04 installed in region us-west-2

4. show and apply the Terraform plan:

terraform init
terraform plan
terraform apply -auto-approve

Hetzner

1. create an API token and export it as HCLOUD_TOKEN environment variable (this is the default environment variable name used by the Hetzner Cloud Terraform provider):

export HCLOUD_TOKEN=<REDACTED>

Notice that the created token is by definition associated with a project in Hetzner Cloud. You can use the "Default" project or create a new one.

2. create an SSH key pair:

# generate the SSH key pair
ssh-keygen -t rsa -b 4096 -C "terraform-hetzner" -q -N "" -f ~/.ssh/hetzner

3. initialize Terraform variables:

cp terraform.tfvars.hetzner terraform.tfvars

This sample configuration will:

• use the previously created SSH private key
• create 2 nodes of type cx11 with Ubuntu 18.04 installed

4. show and apply the Terraform plan:

terraform init
terraform plan
terraform apply -auto-approve

Scaleway

1. retrieve your organization ID and create an API token and export them as SCALEWAY_ORGANIZATION and SCALEWAY_TOKEN environment variables respectively (these are the default environment variable names used by the Scaleway Terraform provider):

export SCALEWAY_ORGANIZATION=<REDACTED>
export SCALEWAY_TOKEN=<REDACTED>

2. create an SSH key pair and add the public key to the SSH Keys in the Scaleway console:

# generate the SSH key pair
ssh-keygen -t rsa -b 4096 -C "terraform-scaleway" -q -N "" -f ~/.ssh/scaleway

# display the public key to add in Scaleway console
cat ~/.ssh/scaleway.pub

3. initialize Terraform variables:

cp terraform.tfvars.scaleway terraform.tfvars

This sample configuration will:

• use the previously created SSH private key
• create 2 nodes of type VC1S with Ubuntu 18.04 installed

4. show and apply the Terraform plan:

terraform init
terraform plan
terraform apply -auto-approve