# Day 63- 90DaysOfDevOps

Hello Learners! Welcome back. In the previous challenge, We understood the concepts of Terraform block, provider block and Resource block and we successfully provisioned a Docker container with the help of a *Docker* provider. In this challenge, we'll be parameterizing the values within the Terraform configuration files with the help of ***Variables.*** Let's start...

### **Terraform Variables:-**

In Terraform, variables are essential for parameterizing and sharing values within Terraform configurations. Variables allow you to make your configuration more dynamic, reusable, and flexible. There are two types of variables we can use with Terraform

* **Input Variable:-** They allow you to pass values into modules or configurations from the outside. Input variables can be defined within a module or at the root level of your configuration.
    
* **Output Variables:-** They allow you to expose values from the module or configuration, making them available for use in other parts of your Terraform setup.
    

### How to Use:-

**1- Directly in Configuration file:-**

You can set default values for your variables directly in your Terraform configuration file or separate the `variable.tf` file from `main.tf` for the variable is as follows.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1697855931072/23a77525-8d16-4091-b895-5c9f21b13156.png align="center")

Or use it in one file i.e. main.tf as follows

```plaintext
variable "amiID" {
	description = "AMI ID for instance in region AP-SOUTH-1"
	type = string
	default = "ami---" #put ami id as required
}

variable "instanceType" {
	description = "Instance type"
	type = string
	default = "t2.micro"  #any as required
}

provider "aws" {
	region = "ap-south-1"
}

resource "aws_instance" "Example" {
	ami = var.amiID
	instance_type = var.instanceType
}
```

**2- From the terminal:-**

You can explicitly change the value of the variable using the `-var` flag with `terraform apply/plan` commands.

Example:- `terraform apply -var "instanceType=t2.medium"`

**3- From** `terraform.tfvars` **file:-**

If you don't want to change the default values provided in a `variable.tf` file but use different values for once, then use `terraform.tfvars` file to store variable values so at the time of execution Terraform uses variable values mentioned in `terraform.tfvars` file directly instead of default variable values.

You must have to use terraform.tfvars file with naming convention. If you customize the name for the `.tfvars` file then you must specify the file while executing the terraform apply/plan command.

`terraform plan/apply -var-file=<custom-name>.tfvars`

OR rename the file as `<custom-name>.auto.tfvars` so no need to use the `-var-file` option.

### Task 1- **Create a simple txt file with Terraform using the variable file.**

Create *main.tf* file as shown below

```plaintext
resource "local_file" "devops" {
    filename = var.filename
    content = var.content
}
```

create *variable.tf* file

```plaintext
variable "filename" {
    default = "/home/ubuntu/terraform/local-file/file.txt"
}

variable "content" {
    default = "Hello, Amit Here!This file is created by terraform script"
}
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1698124965713/44f37d77-16a0-404c-a5e0-fb4e5f9e606f.png align="center")

Use `terraform init` command to initialize with resources and apply after using `terraform apply`.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1698125017322/52c4c151-ac06-4569-a672-7948875d283a.png align="center")

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1698125031990/b0449e35-cae7-404c-83eb-6b8b655e686c.png align="center")

Cross-check changes.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1698125087222/e762dbe3-ea01-4770-86e4-0cf784ced022.png align="center")

## Data Types in Terraform

Terraform supports various data types, each serving a unique purpose and use cases.

### 1- Map

In terraform, a map is a data structure that allows you to store and manage a collection of key-value pairs. Maps are often used to define input variables, output values, and resource configurations.

### **Task 2-**

In the above example we created a file with some content, let's create two different files with different contents using map data type.

Make changes in variable.tf as shown below

```plaintext
variable "filename1" {
    default = "/home/ubuntu/terraform/local-file/file1.txt"
}

variable "filename2" {
    default = "/home/ubuntu/terraform/local-file/file2.txt"
}

variable "content" {
	type = map
    default = {
	"state1" = "This is cool"
	"state2" = "This is cooler"
	}
}
```

make changes in the main.tf file also

```plaintext
resource "local_file" "file1" {
	filename = var.filename1
	content = var.content["state1"]
}

resource "local_file" "file2" {
        filename = var.filename2
        content = var.content["state2"]
}
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1698126265207/db9946ca-ae8a-4e80-b8c8-7590abdfca71.png align="center")

Apply the changes using the `terraform apply` command and check the created files.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1698126339362/1e61a89d-b849-431f-ba59-0dcf98177ae9.png align="center")

### 2- List

A list is a data structure that allows you to store and manage a collection of values. Lists are often used to define input variables, output values, and resource configurations.

### Task 3-

I will create main.tf and variable.tf in different directories to demonstrate this task.

Create variable.tf file as shown below

```plaintext
variable "filename" {
	type = list
	default = ["/home/ubuntu/terraform/list/file1.txt","/home/ubuntu/terraform/list/file2.txt"]
}

variable "content" {
	type = map
    default = {
	"state1" = "This is cool"
	"state2" = "This is cooler"
	}
}
```

Create main.tf as shown below

```plaintext
resource "local_file" "file1" {
	filename = var.filename[0]
	content = var.content["state1"]
}

resource "local_file" "file2" {
        filename = var.filename[1]
        content = var.content["state2"]
}
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1698127254981/cf31d223-192c-4e16-bb06-5c97b8b9749b.png align="center")

Initialize with `terraform init` command.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1698127067356/1c1a37eb-a4d9-4cf0-936c-f25967c3b3c0.png align="center")

Use the `terraform apply` command to provision. Confirm the changes.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1698127309470/6f74f763-7ba8-4e21-b9df-0bf8578585bf.png align="center")

By understanding and effectively utilizing Terraform variables and data types, you enhance your ability to create flexible, maintainable, and robust infrastructure configurations.

Thank you so much for taking the time to read till the end! Hope you found this blog informative.

Feel free to explore more of my content, and don't hesitate to reach out if need any assistance from me or in case of you have any questions.

Find me on:- [**Hashnode**](https://avp23.hashnode.dev/) [**LinkedIn**](http://www.linkedin.com/in/amit-pawar-7b802b265) [**Github**](https://github.com/amitvpawar)

**Happy Learning!**