Terraform: Destroy Infrastructure Explained

Last Updated on July 24, 2024 by Arnav Sharma

When managing cloud infrastructure, understanding the lifecycle of resources is crucial. Terraform, a powerful tool by HashiCorp, simplifies this process. Particularly, the “destroy” command in Terraform is essential when you need to delete or decommission resources. In this blog, we will delve into how to use Terraform to destroy infrastructure, especially focusing on examples from Azure.

What is Terraform?

Terraform, developed by HashiCorp, is an infrastructure as code (IaC) tool used to provision and manage cloud infrastructure. Using a terraform script, you can define, deploy, and update resources across various cloud platforms, including AWS and Azure.

Terraform Workflow: Plan, Apply, and Destroy

The Terraform workflow typically involves three steps:

1. Terraform Plan: Creates an execution plan to determine what actions are necessary to achieve the desired state specified in the terraform configuration files.
2. Terraform Apply: Applies the changes necessary to reach the desired state of the configuration.
3. Terraform Destroy: Used to remove resources that are no longer needed.

Understanding the Destroy Command

The terraform destroy command is a critical part of managing the lifecycle of your infrastructure. It’s used when you want to remove any provisioned infrastructure that you no longer need, helping to reduce your security exposure and manage costs.

How it Works

1. Specify the Script: You start by specifying the terraform script that outlines the infrastructure you wish to remove.
2. Creating a Plan: Terraform then creates a plan showing what will be removed.
3. Execution: Finally, upon approval, Terraform will destroy the specified resources.

Use Cases for Terraform Destroy

• Reducing Costs: When you no longer need infrastructure, destroying it helps reduce costs associated with idle resources.
• Environment Management: For managing short-lived environments like build or test environments, terraform destroy helps in decommissioning them once they are no longer needed.
• Updating Infrastructure: In cases where it’s easier to recreate the infrastructure from scratch rather than updating it, terraform destroy is used to remove the old infrastructure before provisioning new resources.

Destroying Azure Resources with Terraform

Azure, like AWS, can be managed using Terraform. Whether it’s an EC2 instance in AWS or a VM in Azure, Terraform provides a unified way to manage these resources.

Destroying an Azure VM

1. Define the Resource: In your Terraform script, you would have defined an Azure VM.
2. Plan and Apply: You would have initially used terraform plan and terraform apply to provision the VM.
3. Destroy: To remove this VM, you would update your Terraform configuration to reflect that the VM is no longer needed and then run terraform destroy.

Best Practices for Using Terraform Destroy

1. Backup State File: Always backup your Terraform state file before running the destroy command.
2. Review Execution Plan: Carefully review the execution plan created by Terraform to ensure only the intended resources are destroyed.
3. Manage Dependencies: Terraform determines the order of resource destruction based on dependencies. Ensure that your configurations correctly reflect these dependencies.
4. Use Version Control: Store your Terraform configurations in a version control system like GitHub for better management and tracking.

Example 1: Delete a Simple Azure Resource

Suppose you have a Terraform configuration that defines an Azure virtual machine (VM). Here’s how you would typically destroy this VM:

1. Initial Setup: You should have a Terraform script (main.tf) that defines an Azure VM. For example: resource "azurerm_virtual_machine" "example_vm" {
# VM configuration details
}

2. Plan and Apply: Initially, you would use terraform plan and terraform apply to provision this VM.

3. Destroy the VM: When you decide to remove this VM, you would use the terraform destroy command. Here’s how:

   • Open your command line.
   • Navigate to the directory containing your Terraform configuration files.
   • Run the command: terraform destroy
   • Terraform will provide an execution plan and ask for confirmation before destroying the resources.

Example 2: Destroying Specific Resources in Azure

Sometimes, you might want to destroy a specific resource within your Terraform-managed infrastructure without affecting other resources.

1. Identify the Resource: First, identify the resource you want to destroy. Each resource in your Terraform state file has an address. You can list all resources with their addresses using:
terraform state list
2. Destroy the Specific Resource: Use the terraform destroy command with the -target option. For instance, to destroy a specific Azure network interface: terraform destroy -target azurerm_network_interface.example_nic

   This command will only destroy the resource specified and leave others intact

Example 3: Destroying All Resources in a Terraform Project

If you need to completely tear down all the infrastructure managed by a Terraform project, you simply run the terraform destroy command without specifying a target. This is common when decommissioning an entire environment.

1. Execute Terraform Destroy:
   • Navigate to your project directory.
   • Run: terraform destroy
   • Review the plan and confirm the destruction.

FAQ – Terraform

Q: What are the steps to destroy AWS infrastructure using Terraform?

A: To destroy AWS infrastructure using Terraform, you need to follow a series of steps. First, use the Terraform CLI to initiate the process. Begin with the terraform plan step to review the resources defined in your infrastructure and then proceed with the terraform apply step to apply any pending changes. To specifically destroy resources, add a terraform destroy step in your script. This step is independent of any other Terraform processes and is focused on removing the infrastructure deployed. Ensure that you destroy the resources in a suitable order to respect dependencies, especially in complicated cases with multiple resources. The terraform destroy command terminates resources managed by Terraform, created in the previous tutorials, or provisioned using specific Terraform scripts. It’s important to be cautious, as this may remove a production environment from service. Finally, you can continue to the next tutorial once the destruction is complete.

Q: How does HashiCorp’s Terraform interact with AWS for resource management?

A: HashiCorp’s Terraform interacts with AWS for resource management through its infrastructure as code capabilities. Terraform allows you to define and provision AWS infrastructure using a declarative configuration language known as HashiCorp Configuration Language (HCL). When you use Terraform with AWS, it typically involves creating a Terraform script that Harness will use for provisioning. This script includes definitions for resources like AWS EC2 instances. Terraform communicates with AWS through its API, allowing it to create, update, and destroy resources like AWS EC2 instances or other critical resources. For instance, you can use the AWS command line to manage specific resources, such as an IAM role or AWS EC2 instances, directly through Terraform scripts. Terraform ensures that the infrastructure you have provisioned is created and updated according to the specifications in your repository, and it also has the capability to destroy all the resources if needed.

Q: Can Terraform be used to handle complex infrastructure in production environments?

A: Yes, Terraform can be used to handle complex infrastructure in production environments. As a powerful tool by HashiCorp for infrastructure as code, Terraform enables DevOps teams to efficiently manage and provision resources. It’s suitable for handling complicated cases with multiple resources in production environments, allowing you to define, deploy, and update infrastructure in a controlled and predictable manner. Terraform’s ability to manage the lifecycle of infrastructure includes the provision to destroy resources, which is crucial in production environments. For instance, the terraform destroy command can be used to remove any infrastructure, including critical resources, in a production environment, effectively taking it out of service. This is particularly useful when you need to reduce costs or reallocate resources. It’s important for a HashiCorp developer or a Harness developer to understand that while Terraform can manage complex infrastructures, it must be used with caution, especially when the infrastructure involves production environments.

Q: How do you use Terraform CLI to destroy AWS infrastructure in a production environment?

A: To destroy AWS infrastructure in a production environment using Terraform CLI, you first need to run a terraform plan step to identify the resources managed by Terraform. After reviewing the plan, execute the terraform apply step to implement any pending changes. Next, to specifically destroy the infrastructure, add a terraform destroy step in your Terraform script. This step is crucial and must be executed with caution, as it may remove a production environment from service. It’s independent of any other Terraform process and is restricted to removing the infrastructure deployed, including critical resources like AWS EC2 instances. Ensure that you destroy the resources in a suitable order to respect dependencies, particularly in complicated cases with multiple resources.

Q: What are the considerations for a HashiCorp developer when using Terraform to manage AWS resources?

A: As a HashiCorp developer using Terraform to manage AWS resources, it’s important to understand the implications of each step in the Terraform provisioning process. When working with Terraform infrastructure, consider using the Terraform CLI and the Harness Developer Hub for efficient management. For instance, the terraform plan and apply steps are crucial for creating and updating infrastructure. However, when you need to destroy resources, especially in a production environment, the terraform destroy step becomes critical. This step terminates resources managed by Terraform and should be used judiciously to avoid unintended consequences. In scenarios where you must remove any infrastructure, such as in a repository, ensure that the terraform destroy command is executed with a clear understanding of its impact. This is particularly important in critical or restricted environments where removing infrastructure can have significant effects.

Q: How does Harness integrate with Terraform for infrastructure management and provisioning?

A: Harness integrates with Terraform for infrastructure management and provisioning by providing a platform that facilitates the use of Terraform scripts. In this integration, Harness acts as a delegate, using Terraform scripts for provisioning and managing infrastructures such as AWS EC2 instances. A typical workflow involves creating a Terraform script that Harness will use for provisioning, which includes defining the infrastructures you have provisioned. The Terraform provisioner in Harness allows you to automate the deployment and management of your infrastructure. This includes the ability to add a terraform destroy step to remove any provisioned infrastructure, particularly useful in production environments or when you need to reduce costs. Harness Terraform integration is especially beneficial in managing and destroying resources defined in the previous tutorials, ensuring a streamlined process for infrastructure management.

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