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Terraform basics using AWS

Taken from the main tutorial: https://developer.hashicorp.com/terraform/tutorials/aws-get-started from step 2 onward.

The example explain how to create and update an EC2 with basic properties.

We start using local state (the cli generate ".tfstate" files locally) that must NOT be checked in git, and ignored from a VCS because they can contains secrets and sensitive data from our cloud account.

At the ends of the tutorial, we could use the state for free on terraform cloud and test run this sample.

Key points

Here is a list of the main points showed following the tutorial:

  • basic terraform commands: init, fmt, validate, show, plan, apply, destroy
  • update a terraform template
  • variables usage and reference in the main template
  • outputs (like CF/CDK outputs) from AWS to show EC2 instance id, public ip v4 for example
  • attach terraform cloud to handle state remotely instead of locally

Basic terraform commands

Terraform cli commands used in the tutorial:

init

installs / update current modules and providers

fmt

format all tf files

validate

validate the template files

show

show the current template state, if deployed on AWS we could see the status of the EC2 instance

plan

plan checks and infer what to do on AWS, explain the planning

apply

run on AWS the current template files

destroy

delete the current state (if local) or in terraform cloud, remove the created AWS resources.

Update a terraform template

For ex changing instance type or ami ID and see the changes re-applying the template

Variables

Creating a file variables.tf we can setup variabiles as inputs for the main template.

They can be referenced from the template using "var." or from the cli using -var ... flag.

Variables have a description, a type (string, bool, number, list, map), a default value

Outputs

Like in Cloudformation and CDK, we can export some specific computed values from our resources deployed on the cloud, for ex EC2 instance id, and so on.

Terraform cloud usage

We then create a terraform cloud account and configure it with an access token using the command: terraform login. Then create a CLI workspace, setup some variables as ENV variables + sensitive for AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY under the new workspace.

Change the template adding the organization and workspace to use, then we can see that all infra plannings and deploys will run (and also the terraform state will be saved) on terraform cloud.

run again terraform init to fetch terraform cloud modules.

Then you could run terraform plan / apply to see in the website the updated state, and the queued runs for deploying the infra remotely from their cloud.

nice to see: state changes like apply / update / destroy have diff like in the UI.