Terraform.md

Terraform

Overview

1. Create multiple cloud / online apps, link and configure them
2. Infrastructure as Code (IaC)
3. Sandbox: https://developer.hashicorp.com/terraform/sandbox
4. Terraform loads all .tf files in the same folder together

---

HCL Syntax

Comments

/* multi-line comment */
# single-line comment

Block Structure :

my_block {
  key1 = "value"      # string
  key2 = 3            # integer
  key3 = true         # boolean
  key4 = [1, 2, 3]    # list
  key5 = { k = "v" } # map
}

• Everything is a block
• Main Blocks are provider, resource , variable , output , locals
  • Provider :
    • Download Libarary
    • Copy from Terraform Doc
    • Eg: provider "git_hub"{}
    • Can be in main.tf / providers.tf
  • Resource
    • Config Library
    • Copy from Terraform Doc
    • should be in main.tf
  • variable
    • Input values from user
    • variables.tformain.tf`
    • Eg: variable "a"{default = 1}
    • Access by "var.a"
  • output
    • print putput
    • outputs.tformain.tf`
    • Eg: output "my_output" {value = var.a}
  • locals
    • Interal Values
    • locals.tformain.tf`
    • eg locals{k="v"}
    • Access by local.k
  • Others
    • module {} : Functions
    • terraform {} : Terraform Backend Settings

---

Variables, Locals, Outputs

Variable

• Input from user
• Access using var.name
• Interpolation: ${var.name}

variable "a" {
  default = 1
}

• Pass via CLI :

variable "a" {
  
} /* blank*/

terraform plan -var="a=1"

• Using tfvars file (prod.tfvars):

a = 1

terraform plan -var-file="prod.tfvars"

• Using environment variable:

export TF_VAR_a=1

Locals

• For internal usage

locals {
  name    = "Deepak"
  message = "HI ${local.name}"
}

Output

• Display values after apply

output "my_output" {
  value = resource_name.attribute
}

---

Condition (Using count)

resource "local_file" "pet" {
  count    = fileexists("./pets.txt") ? 0 : 1
  filename = "./pets.txt"
  content  = "HI"
}

---

Functions

• Built-in functions:

  • Numeric
  • String
  • List / Collection
  • DateTime
  • File
  • Conversion

---

Resource Dependency

resource "aws_instance" "a1" {
  key = "val"
}

resource "aws_instance" "a2" {
  key = aws_instance.a1.key
}

---

1. Example: Print Env

# $export TF_VAR_test_var="123"
#main.tf 
output { value =var.test_var}
variable test_var{}


# terraform init
# terraform validate
# terraform plan
# terraform apply
# terraform destroy

---

2. Example: Create Sample File

# Create file main.tf and add below

resource "local_file" "pet" {
  filename = "./pets.txt"
  content  = "HI"
}

Commands:

terraform init
terraform validate
terraform plan
terraform apply
terraform destroy -target=local_file.pet

---

3. Example: Create GitHub Repository Single File

# create main.tf

/*1.Import and Setup : Copy from Terraform Website */
provider "github" {
  token = var.terraform_git_token
}

/*2.Env variable  */
variable "terraform_git_token" {}
#$export TF_VAR_terraform_git_token="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"


/*3.Config :  Copy from Terraform Website */
resource "github_repository" "my_git_resrc" {
  name        = var.git_repo_name
  description = local.git_description
  visibility = "public"
}

/*4.Input from CLI  */
variable "git_repo_name"{
}

/*5. local*/
locals{
git_description ="terraform_git_description"
}


# terraform init
# terraform validate
# terraform plan
# terraform apply
# terraform destroy