Terraform Input Variables

Terraform supports several types of variables, which allow you to customize and manage your infrastructure configurations more effectively. Below are the types of variables.

Terraform Input Variables

It allow you to customize the behavior of your Terraform modules without modifying the source code. Below are the way to declare or pass the variable to terraform resources.

• Declaration: Using the variable block. In the variable block define type, description and default value.

    variable "Variable_name" {
      description = ""
      type        = string # Type of variable
      default     = "us-east-1" # Any default value
    }
    }
  

• Usage: Accessed using the var keyword, e.g., var.instance_type

  Lets create versions.tf, variables.tf, security-groups.tf, ec2-instance.tf

  version.tf

    # Terraform Block
    terraform {
      required_version = ">= 1.7"
      required_providers {
        aws = {
          source  = "hashicorp/aws"
          version = "~> 4.0"
        }
      }
    }
  
    # Provider Block
    provider "aws" {
      region  = var.aws_region
      profile = "default"
    }
  

  variables.tf

    variable "aws_region" {
      description = "Region name"
      type        = string
      default     = "us-east-1"
    }
  
    variable "ec2_ami_id" {
      description = "AMI name of ec2"
      type        = string
      default     = "ami-0915bcb5fa77e4892"
    }
  
    variable "ec2_instance_count" {
      description = "EC2 Count"
      type        = number
      default     = 1
    }
  

  security-groups.tf

    # Create Security Group - SSH Traffic
    resource "aws_security_group" "MY-SG-SSH" {
      name        = "vpc-ssh"
      description = "MY Security group"
      ingress {
        description = "Allow SSH Port"
        from_port   = 22
        to_port     = 22
        protocol    = "tcp"
        cidr_blocks = ["0.0.0.0/0"]
      }
      egress {
        description = "Allow all IP and port outbond"
        from_port   = 0
        to_port     = 0
        protocol    = -1
        cidr_blocks = ["0.0.0.0/0"]
      }
    }
  
    # Create Security Group - WEB Traffic
    resource "aws_security_group" "MY-SG-WEB" {
      name        = "vpc-web"
      description = "Security group for web"
  
      ingress {
        description = "Allow port 80"
        from_port   = 80
        to_port     = 80
        protocol    = "tcp"
        cidr_blocks = ["0.0.0.0/0"]
      }
  
      ingress {
        description = "Allow port 443"
        from_port   = 443
        to_port     = 443
        protocol    = "tcp"
        cidr_blocks = ["0.0.0.0/0"]
      }
  
      egress {
        description = "Allow all IP and port outbound"
        from_port   = 0
        to_port     = 0
        protocol    = -1
        cidr_blocks = ["0.0.0.0/0"]
      }
    }
  

  ec2-instance.tf

    # Create EC2 Instance
    resource "aws_instance" "MY-EC2-VM" {
      ami                    = var.ec2_ami_id
      instance_type          = "t2.micro"
      key_name               = "terraform-key"
      count                  = var.ec2_instance_count
      vpc_security_group_ids = [aws_security_group.MY-SG-SSH.id, aws_security_group.MY-SG-WEB.id]
      tags = {
        "Name" = "My ec2 vm"
      }
      user_data = <<-EOF
        #!/bin/bash
        sudo yum update -y
        sudo yum install httpd -y
        sudo systemctl enable httpd
        sudo systemctl start httpd
        echo "<h1>Welcome ! AWS Infra created using Terraform in us-east-1 Region</h1>" > /var/www/html/index.html
        EOF
    }
  

• Provide Input Variables when prompted during terraform plan or apply

  Lets add one new variable instance type ec2_instance_type without any default value

• v3: Override default variable values using CLI argument -var

• v4: Override default variable values using Environment Variables

• v5: Provide Input Variables using terraform.tfvars files

• v6: Provide Input Variables using <any-name>.tfvars file with CLI argument -var-file

• v7: Provide Input Variables using auto.tfvars files

• v8-01: Implement complex type constructors like list

• v8-02: Implement complex type constructors like maps

• v9: Implement Custom Validation Rules in Variables

• v10: Protect Sensitive Input Variables

• v11: Understand about File function