Running Local Programs with Terraform's local-exec Provisioner

Terraform's primary function is infrastructure provisioning and management. However, it can also execute local programs on your machine using the local-exec provisioner. This functionality allows you to integrate pre- or post-deployment tasks into your Terraform workflow.

Using the local-exec Provisioner

The local-exec provisioner enables you to run commands on the machine where Terraform is executing, not on the provisioned resources themselves. Here's the basic syntax:

resource "<resource_type>" "<resource_name>" {
  # ... other resource configuration options

  provisioner "local-exec" {
    command = "<command_to_execute>"
  }
}

• <resource_type>: The type of Terraform resource you're configuring (e.g., aws_instance, null_resource).
• <resource_name>: A unique name for the resource.
• <command_to_execute>: The shell command you want to run locally.

Example:

resource "null_resource" "post_deploy_tasks" {

  provisioner "local-exec" {
    command = "sh post_deployment.sh"
  }
}

This configuration defines a null_resource named "post_deploy_tasks" with a local-exec provisioner. The command argument points to a script (post_deployment.sh) containing the local tasks you want to execute after resource creation.

Key Points:

• The local-exec provisioner runs commands with the same user permissions as Terraform itself.
• You can use environment variables within the command argument for dynamic behavior.
• The local-exec provisioner typically runs after the resource is created.

Benefits of Using local-exec

• Automating Local Tasks: Integrate tasks like script execution, file manipulation, or code generation into your Terraform workflow.
• Improved Workflow: Streamline your infrastructure provisioning process by automating pre- or post-deployment steps.

Considerations

• Security: Be cautious when using local-exec as it runs with Terraform's permissions.
• Limited Scope: This provisioner is not intended for long-running processes or complex operations.

For advanced local file manipulation or system administration tasks, consider dedicated tools outside of Terraform.

By leveraging the local-exec provisioner effectively, you can extend your Terraform configurations to automate additional tasks and enhance your infrastructure provisioning workflow.