# Terraform Basics

Terraform is an open-source Infrastructure as Code (IaC) tool developed by HashiCorp. It allows users to define, provision, and manage infrastructure across various cloud providers (like AWS, Azure, and GCP) and on-premises environments using a declarative configuration language known as **HCL (HashiCorp Configuration Language)**.

Terraform is popular because:

* It supports multiple cloud providers (AWS, Azure, Google Cloud).
    
* It provides a unified workflow.
    
* It maintains an infrastructure state file to track resources.
    
* It uses a modular approach to manage complex systems.
    

---

### **Key Terraform Commands**

Here are the most common terraform commands you will run into:

#### 1\. `terraform init`

* **Purpose**: Prepares the working directory for Terraform operations.
    
* **What it does**:
    
    * Downloads provider plugins.
        
    * Initializes the backend for storing the Terraform state.
        
    * Verifies the configuration files.
        

#### 2\. `terraform validate`

* **Purpose**: Checks the configuration files for syntax or logical errors.
    
* **What it does**:
    
    * Ensures that the configuration is syntactically valid.
        
    * Validates against the provider's schema but does not connect to the cloud.
        

#### 3\. `terraform fmt`

* **Purpose**: Formats the configuration files to match the standard style conventions.
    
* **What it does**:
    
    * Ensures consistent indentation and spacing.
        
    * Makes code easier to read and maintain.
        

#### 4\. `terraform plan`

* **Purpose**: Creates an execution plan showing what actions Terraform will take.
    
* **What it does**:
    
    * Highlights the changes required to achieve the desired state.
        
    * Outputs actions like resource additions, modifications, or deletions without applying them.
        

#### 5\. `terraform apply`

* **Purpose**: Executes the actions defined in the execution plan created by `terraform plan`.
    
* **What it does**:
    
    * Creates, updates, or deletes resources in the infrastructure.
        
    * Requires user confirmation before execution unless the `-auto-approve` flag is used.
        

#### 6\. `terraform plan -destroy`

* **Purpose**: Simulates the destruction of resources without actually executing it.
    
* **What it does**:
    
    * Generates a plan detailing which resources will be removed.
        
    * Useful for previewing the impact of a `terraform destroy` command.
        

#### 7\. `terraform destroy`

* **Purpose**: Removes all resources defined in the Terraform configuration.
    
* **Note**: Always run `terraform plan -destroy` before running any `terraform destroy`
    
* **What it does**:
    
    * Deletes the infrastructure safely and ensures resources are destroyed in the correct order.
        
    * You can also target specific resources using the **target** flag instead of destroying all the resources.
        
    * eg. `terraform destroy --target aws_instance.instance_name`
        

#### 8\. `terraform import`

* **Purpose**: Brings existing infrastructure into Terraform's management.
    
* **What it does**:
    
    * Adds resources not originally created with Terraform to the state file.
        
    * Does not generate configuration files automatically; you must write the configuration manually.