Basic Usage

terraform init

• Downloads the code for the stated providers in the main.tf.
• Downloads additional modules leveraged.

State File

• Terraform’s representation of the world.
• JSON file containing information about every resource and data object.
• Contains Sensitive Info (e.g. database password) - DO NOT COMMIT THIS.
• Can be stored locally or remotely.

Local Backend

You install Terraform on your local machine, along with the Terraform State file.

The Good:

• Simple to get started.

The Bad:

• Sensitive data is stored in plain text.
• Uncollaborative.
• Manual.

Remote Backend

Could leverage Terraform Cloud or self-host (Amazon S3).

The Good:

• Sensitive data is encrypted.
• Collaboration is possible.
• Automation is now possible (CI/CD).

The Bad:

• Increased complexity.

Terraform Cloud:

terraform {
    backend "remote" {
        organization = "your-org"

        workspaces {
            name = "your-workspace"
        }
    }
}

• Free up to 5 users.

AWS:

terraform {
    backend "s3" {
        bucket = "bucket_name"
        key = "key_for_bucket"
        region = "us-east-1"
        dynamodb_table = "terraform-state-locking"
        encrypt = true
    }
}

• S3 Bucket used for storage.
• DynamoDB used for locking (race condition with multiple users).

But…

• You can’t provision this if you don’t have a Terraform state.

So you can…

1. Bootstrap it
   • No Remote Backend Specified (defaults to local).
   • Define the resources needed.
   • Run terraform apply to apply them to AWS.
   • Now change the backend back to AWS remote.
   • Keep the specified resources, run terraform init again, it migrates local to remote.

terraform plan

• Looks at the Terraform Config (Desired State) and compares it to the Terraform State (Actual State).
• Finds the discrepancies between the two sates, and leverages a provider to make the desired state the actual state.

terraform destroy

• Plan: Destroy Everything.
• You only do this when you never need that project back.