Using -var with Terraform plan through the CLI

Introduction

The -var option is a popular way to pass variables directly to Terraform commands like terraform plan. But when using remote backend, you may get some error like "Run variables are currently not supported" while passing -var option in terraform plan. This is because The "remote" backend does not support setting run variables at this time. Currently the only to way to pass variables to the remote backend is by creating a '*.auto.tfvars' variables file. Additionally you can also set variables on the workspace in the web UI.

Scenario
When a user tries to use -var option in terraform plan while using remote backend.

For example:

terraform plan -var="example_variable_name=value"

Error:
Run variables are currently not supported

Things to Consider Before Using the -var Option

1. Terraform Version:

   • Versions below 1.1 do not support direct usage of -var with remote backends.

   • Versions 1.1 and higher introduce the cloud block, which enables the use of -var directly in CLI commands.

2. Backend Configuration:
   • For remote backends, the -var option is not directly supported. You must rely on other methods to define variables.
   • For cloud block configurations, the -var option can be used without restrictions in Terraform CLI commands.
3. Alternative Methods for Variable Management:
   • Use *.auto.tfvars files: These files allow you to define variables that are automatically loaded during Terraform runs.
   • Set workspace variables: Define variables directly in Terraform Enterprise or Terraform Cloud for a centralized and consistent approach.

Solution:

For Terraform Versions Below 1.1

1. Create a *.auto.tfvars file containing your variables.
   Example:
   example_variable_name = "value"
2. Alternatively, define workspace variables in the Terraform Enterprise or Cloud UI, ensuring they are accessible during runs.

For Terraform Versions 1.1 and Higher

Leverage the cloud block to pass variables directly with the -var option during terraform plan.

Example Command:

This setup simplifies workflows and eliminates the need for additional variable files or workspace configurations.

Additional Information

• https://developer.hashicorp.com/terraform/language/backend/remote