Terraform Settings, Providers & Resource Blocks¶

Step-01: Introduction¶

Terraform Settings
Terraform Providers
Terraform Resources
Terraform File Function
Create EC2 Instance using Terraform and provision a webserver with userdata.

Step-02: In c1-versions.tf - Create Terraform Settings Block¶

Understand about Terraform Settings Block and create it

terraform {
  required_version = "~> 0.14" # which means any version equal & above 0.14 like 0.15, 0.16 etc and < 1.xx
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.0"
    }
  }
}

Step-03: In c1-versions.tf - Create Terraform Providers Block¶

Understand about Terraform Providers
Configure AWS Credentials in the AWS CLI if not configured
```
# Verify AWS Credentials
cat $HOME/.aws/credentials
```

Create AWS Providers Block

# Provider Block
provider "aws" {
  region  = us-east-1
  profile = "default"
}

Step-04: In c2-ec2instance.tf - Create Resource Block¶

Understand about Resources
Create EC2 Instance Resource
Understand about File Function
Understand about Resources - Argument Reference

Understand about Resources - Attribute Reference

# Resource: EC2 Instance
resource "aws_instance" "myec2vm" {
  ami = "ami-0533f2ba8a1995cf9"
  instance_type = "t3.micro"
  user_data = file("${path.module}/app1-install.sh")
  tags = {
    "Name" = "EC2 Demo"
  }
}

Step-05: Review file app1-install.sh¶

#! /bin/bash
# Instance Identity Metadata Reference - https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-identity-documents.html
sudo yum update -y
sudo yum install -y httpd
sudo systemctl enable httpd
sudo service httpd start  
sudo echo '<h1>Welcome to StackSimplify - APP-1</h1>' | sudo tee /var/www/html/index.html
sudo mkdir /var/www/html/app1
sudo echo '<!DOCTYPE html> <html> <body style="background-color:rgb(250, 210, 210);"> <h1>Welcome to Stack Simplify - APP-1</h1> <p>Terraform Demo</p> <p>Application Version: V1</p> </body></html>' | sudo tee /var/www/html/app1/index.html
sudo curl http://169.254.169.254/latest/dynamic/instance-identity/document -o /var/www/html/app1/metadata.html

Step-06: Execute Terraform Commands¶

# Terraform Initialize
terraform init
Observation:
1) Initialized Local Backend
2) Downloaded the provider plugins (initialized plugins)
3) Review the folder structure ".terraform folder"

# Terraform Validate
terraform validate
Observation:
1) If any changes to files, those will come as printed in stdout (those file names will be printed in CLI)

# Terraform Plan
terraform plan
Observation:
1) No changes - Just prints the execution plan

# Terraform Apply
terraform apply 
[or]
terraform apply -auto-approve
Observations:
1) Create resources on cloud
2) Created terraform.tfstate file when you run the terraform apply command

Step-07: Access Application¶

Important Note: verify if default VPC security group has a rule to allow port 80

# Access index.html
http://<PUBLIC-IP>/index.html
http://<PUBLIC-IP>/app1/index.html

# Access metadata.html
http://<PUBLIC-IP>/app1/metadata.html

Step-08: Terraform State - Basics¶

Understand about Terraform State
Terraform State file terraform.tfstate
Understand about Desired State and Current State

Step-09: Clean-Up¶

# Terraform Destroy
terraform plan -destroy  # You can view destroy plan using this command
terraform destroy

# Clean-Up Files
rm -rf .terraform*
rm -rf terraform.tfstate*

Step-10: Additional Observations - Concepts we will learn in next section¶

EC2 Instance created we didn't associate a EC2 Key pair to login to EC2 Instance
Terraform Resource Argument - Key Name
AMI Name is static - How to make it Dynamic ?
Use Terraform Datasources concept
We didn't create multiple instances of same EC2 Instance
Resource Meta-Argument: count
We didn't add any variables for parameterizations
Terraform Input Variable Basics
We didn't extract any information on terminal about instance information
Terraform Outputs
Create second resource only after first resource is created
Defining Explicit Dependency in Terraform using Resource Meta-Argument depends_on
WE ARE GOING TO LEARN ALL THE ABOVE CONCEPTS IN NEXT SECTION