Terraform – Notes – Day 2 – August

terraform init
terraform validate
terraform plan
terraform apply
terraform show
terraform output
terraform destory

Training Material

• https://devopsschool.com/slides/terraform/index.html
• https://www.devopsschool.com/blog/?s=terraform
• Recording

Revision

• What is Terraform?
• Terraform installation
• Terraform Basic Workflow
• Terraform Variables

Variables Labs

variable "instance_count" {
  type = number
  default = 1
}

resource "aws_instance" "example" {
  count = var.instance_count
  ami           = "ami-053b0d53c279acc90"
  instance_type = "t2.micro"
}

variable "instance_name" {
  type = string
  default = "my-instance"
}

resource "aws_instance" "example-number" {
  count = var.instance_count
  ami           = "ami-053b0d53c279acc90"
  instance_type = "t2.micro"
}


variable "security_groups" {
  type = list(string)
  default = ["sg-0541801a7a059ba17"]
}


resource "aws_instance" "example-list" {
  ami           = "ami-053b0d53c279acc90"
  instance_type = "t2.micro"
  vpc_security_group_ids = var.security_groups
}

variable "instance_tags" {
  type = map(string)
  default = {
    Name = "my-instance"
  }
}

resource "aws_instance" "example-map" {
  ami           = "ami-053b0d53c279acc90"
  instance_type = "t2.micro"
  tags = var.instance_tags
}

variable "create_vm" {
  description = "If set to true, it will create vm"
   type   = bool
}

resource "aws_instance" "example-bool" {
  count   = var.create_vm ? 1 : 0
  ami           = "ami-053b0d53c279acc90"
  instance_type = "t2.micro"
  tags = var.instance_tags
}

How to set conditions in Terraform?

How to set conditions in Terraform?
https://www.devopsschool.com/blog/terraform-conditioning-example-program

GLOBAL ARGUMENT == Meta Arugumnets OF each Resources

https://www.devopsschool.com/blog/terraform-tutorials-meta-arguments
https://developer.hashicorp.com/terraform/language/meta-arguments/depends_on

resources
		arg1=value
		arg2=value
		arg3=value
		count
		for_each
		depends_on	
				implicit
				explicit

res1 should exec
		if some vars are set or 

variable "create_instance" {
  description = "If set to true, it will create vm"
   type   = bool
}

resource "aws_instance" "example-expressor" {
  ami           = "ami-053b0d53c279acc90"
  instance_type = "t2.micro"
  count         = var.create_instance ? 1 : 0

  tags = {
    Name = "My EC2 Instance"
  }
}

variable "instance_type" {
  default = "t2.micro"
}

resource "aws_instance" "example-depends-on" {
  ami           = "ami-053b0d53c279acc90"
  instance_type = var.instance_type

  tags = {
    Name = "My EC2 Instance"
  }
}

resource "aws_s3_bucket" "example_bucket" {
  depends_on = [aws_instance.example-depends-on]
  bucket     = "my-unique-bucket-name-dksjdhsakjdhakjhdkj"
  acl        = "private"
}

How to loop / iterate in Terraform?

• count
• for_each
  https://www.devopsschool.com/blog/how-to-do-looping-iterations-in-terraform/

resource "aws_instance" "example" {
  count = 2
  ami = "ami-053b0d53c279acc90"
  instance_type = "t2.micro"
}

variable "repo-name" {
   type = map
  default = {
      "repo1" = "devops1"
      "repo2" = "devops2"
      "repo3" = "devops3"
}
}

resource "github_repository" "repogithub" {
  for_each = var.repo-name
  name = "${each.value}-devopsschool-xyz"
}

each.key
each.value

Provisonar

Provisonar
----------------------------
https://developer.hashicorp.com/terraform/language/resources/provisioners/syntax
Terraform provisioners Tutorials and Complete Guide

Terrafrom – Example Code for remote-exec, local-exec & file provisioner

file
remote-exec
local-exec


What is User Data and Custom data?
-------------------------------------
Ansible | Chef | Puppet? -----> Configuring servers



resource "aws_instance" "first-ec2" {
  ami           = "ami-053b0d53c279acc90" # us-west-2
  instance_type = "t2.micro"
  key_name 		= "ansiblesunday"
  tags = {
    Name = "RajeshKumar"
  }
  
  connection {
      type     = "ssh"
      user     = "ubuntu"
      private_key = file("ansiblesunday.pem")
      #host = aws_instance.web.public_ip
      host = self.public_ip
  }

  provisioner "local-exec" {
    command = "mkdir devopsschool-local"
  }
  
  provisioner "remote-exec" {
    inline = [
	  "sudo apt-get update",
      "sudo apt-get install apache2 -y",
	  "sudo systemctl start apache2",
    ]
  }
  
  provisioner "file" {
    source      = "providers.tf"
    destination = "/tmp/providers.tf"
  } 
}

Module

===========================================
https://www.devopsschool.com/blog/terraform-modules-tutorials-and-complete-guide/
Terraform Modules explained!!!

Decide factor to write Terraform Module or not?

How to use one module’s variable in another module in terraform?

Dir
	contains
		main.tf
			mod dir1
			mod dir2
			
		1.tf
		2.tf
		3.tf
		tfvars
		dir2 = app
			1.tf
			2.tf
			3.tf
			tfvars
		dir3 == db
			1.tf
			2.tf
			3.tf
			tfvars
		dir4 ==  vpc
			1.tf
			2.tf
			3.tf
			tfvars
==================================
	ROOT MODULE
	CHILE MODULE

===============================================
		Develop your own Module
		Use a Module dev by Someone else ------>


VPC
SUBNET
ROUTET
IGW
NATGW
SECGR
VPN
----------------
learn --> Code -> test -> USE It ENV


===========MAIN.TF=========
module "appserver" {
  source = "./db"
}

module "dbserver" {
  source = "./app"
}

module "vpc" {
  source = "terraform-aws-modules/vpc/aws"

  name = "my-rajesh"
  cidr = "10.0.0.0/16"

  azs             = ["us-east-1a", "us-east-1b", "us-east-1c"]
  private_subnets = ["10.0.1.0/24", "10.0.2.0/24", "10.0.3.0/24"]
  public_subnets  = ["10.0.101.0/24", "10.0.102.0/24", "10.0.103.0/24"]

  enable_nat_gateway = false
  enable_vpn_gateway = false

  tags = {
    Terraform = "true"
    Environment = "dev"
  }
}