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Terraform Variables and Configuration

Terraform Variables and Configuration

There are two ways to configure Terraform runs in Atlas – with Terraform variables or environment variables.

Terraform Variables

Terraform variables are first-class configuration in Terraform. They define the parameterization of Terraform configurations and are important for sharing and removal of sensitive secrets from version control.

Variables are sent to Atlas with terraform push. Any variables in your local .tfvars files are securely uploaded to Atlas. Once variables are uploaded to Atlas, Terraform will prefer the Atlas-stored variables over any changes you make locally. Please refer to the Terraform push documentation for more information.

You can also add, edit, and delete Terraform variables via Atlas. To update Terraform variables in Atlas, visit the "variables" page on your environment.

The maximum size for the value of Terraform variables is 256kb.

For detailed information about Terraform variables, please read the Terraform variables section of the Terraform documentation.

Environment Variables

Environment variables are injected into the virtual environment that Terraform executes in during the plan and apply phases.

You can add, edit, and delete environment variables from the "variables" page on your environment.

Additionally, the following environment variables are automatically injected by Atlas. All Atlas-injected environment variables will be prefixed with ATLAS_

ATLAS_TOKEN - This is a unique, per-run token that expires at the end of run execution (e.g. "abcd.atlasv1.ghjkl...").
ATLAS_RUN_ID - This is a unique identifier for this run (e.g. "33").
ATLAS_CONFIGURATION_NAME - This is the name of the configuration used in this run. Unless you have configured it differently, this will also be the name of the environment (e.g "production").
ATLAS_CONFIGURATION_SLUG - This is the full slug of the configuration used in this run. Unless you have configured it differently, this will also be the name of the environment (e.g. "company/production").
ATLAS_CONFIGURATION_VERSION - This is the unique, auto-incrementing version for the Terraform configuration (e.g. "34").
ATLAS_CONFIGURATION_VERSION_GITHUB_BRANCH - This is the name of the branch that the associated Terraform configuration version was ingressed from (e.g. master).
ATLAS_CONFIGURATION_VERSION_GITHUB_COMMIT_SHA - This is the full commit hash of the commit that the associated Terraform configuration version was ingressed from (e.g. "abcd1234...").
ATLAS_CONFIGURATION_VERSION_GITHUB_TAG - This is the name of the tag that the associated Terraform configuration version was ingressed from (e.g. "v0.1.0").

For any of the GITHUB_ attributes, the value of the environment variable will be the empty string ("") if the resource is not connected to GitHub or if the resource was created outside of GitHub (like using terraform push).

Managing Secret Multi-Line Files

Atlas has the ability to store multi-line files as variables. The recommended way to manage your secret/sensitive multi-line files (private key, SSL cert, SSL private key, CA, etc.) is to add them as Terraform Variables or Environment Variables in Atlas.

Just like secret strings, it is recommended that you never check in these multi-line secret files to version control by following the below steps.

Set the variables in your Terraform template that resources utilizing the secret file will reference:

variable "private_key" {}

resource "aws_instance" "example" {
  ...

  provisioner "remote-exec" {
    connection {
      host         = "${self.private_ip}"
      private_key  = "${var.private_key}"
    }

    ...
  }
}

terraform push any "Terraform Variables" to Atlas:

$ terraform push -name $ATLAS_USERNAME/example -var "private_key=$MY_PRIVATE_KEY"

terraform push any "Environment Variables" to Atlas:

$ TF_VAR_private_key=$MY_PRIVATE_KEY terraform push -name $ATLAS_USERNAME/example

Alternatively, you can add or update variables manually by going to the "Variables" section of your Atlas Environment and pasting the contents of the file in as the value.

Now, any resource that consumes that variable will have access to the variable value, without having to check the file into version control. If you want to run Terraform locally, that file will still need to be passed in as a variable in the CLI. View the Terraform Variable Documentation for more info on how to accomplish this.

A few things to note...

The .tfvars file does not support multi-line files. You can still use .tfvars to define variables, however, you will not be able to actually set the variable in .tfvars with the multi-line file contents like you would a variable in a .tf file.

If you are running Terraform locally, you can pass in the variables at the command line:

$ terraform apply -var "private_key=$MY_PRIVATE_KEY"
$ TF_VAR_private_key=$MY_PRIVATE_KEY terraform apply

You can update variables locally by using the -overwrite flag with your terraform push command:

$ terraform push -name $ATLAS_USERNAME/example -var "private_key=$MY_PRIVATE_KEY" -overwrite=private_key
$ TF_VAR_private_key=$MY_PRIVATE_KEY terraform push -name $ATLAS_USERNAME/example -overwrite=private_key

Notes on Security

Terraform variables and environment variables in Atlas are encrypted using Vault and closely guarded and audited. If you have questions or concerns about the safety of your configuration, please contact our security team at security@hashicorp.com.

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Terraform Variables and Configuration