Define Terraform as per your learning

What is Terraform?

Terraform is an open-source infrastructure as code (IaC) tool created by HashiCorp. It allows users to define and provision data center infrastructure using a declarative configuration language known as HashiCorp Configuration Language (HCL). Terraform can manage resources across various service providers, such as public clouds (e.g., AWS, Azure, GCP), private clouds, and even SaaS services.

How Terraform Works?

Terraform works by reading configuration files that describe the desired state of infrastructure and then applying these configurations to manage the actual infrastructure. Here’s a high-level overview of how Terraform works:

1. Write Configuration: You define your infrastructure in configuration files using HCL. These files describe the resources needed, such as servers, databases, and networking components.
2. Initialize: Terraform initializes the working directory containing the configuration files. This step downloads the provider plugins needed for the defined infrastructure.
3. Plan: Terraform creates an execution plan, which shows the user what actions will be taken to reach the desired state defined in the configuration files. It does this by comparing the current state with the desired state.
4. Apply: Terraform executes the actions proposed in the plan to create, update, or delete infrastructure resources.
5. Manage: Terraform continuously manages and updates the infrastructure as the configuration files change. It keeps track of the current state of the infrastructure in a state file.

Top 5 Terraform Commands

1. terraform init: Initializes a working directory containing Terraform configuration files. This command downloads the necessary provider plugins and sets up the environment. terraform init
2. terraform plan: Creates an execution plan, which shows the changes that will be made to the infrastructure based on the configuration files. terraform plan
3. terraform apply: Applies the changes required to reach the desired state of the configuration. It creates or updates the infrastructure. terraform apply
4. terraform destroy: Destroys the infrastructure managed by the configuration files. This command is used to clean up all resources defined in the configuration. terraform destroy
5. terraform validate: Validates the configuration files for syntax errors and other issues. This command helps ensure that the configuration is syntactically correct. terraform validate

Sample Terraform Code for AWS

Here’s a sample Terraform configuration to create an EC2 instance in AWS:

# Provider configuration
provider "aws" {
  region = "us-west-2"
}

# Create a VPC
resource "aws_vpc" "example_vpc" {
  cidr_block = "10.0.0.0/16"
}

# Create a subnet
resource "aws_subnet" "example_subnet" {
  vpc_id            = aws_vpc.example_vpc.id
  cidr_block        = "10.0.1.0/24"
  availability_zone = "us-west-2a"
}

# Create an Internet Gateway
resource "aws_internet_gateway" "example_igw" {
  vpc_id = aws_vpc.example_vpc.id
}

# Create a route table
resource "aws_route_table" "example_route_table" {
  vpc_id = aws_vpc.example_vpc.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.example_igw.id
  }
}

# Associate the route table with the subnet
resource "aws_route_table_association" "example_route_table_assoc" {
  subnet_id      = aws_subnet.example_subnet.id
  route_table_id = aws_route_table.example_route_table.id
}

# Create a security group
resource "aws_security_group" "example_sg" {
  vpc_id = aws_vpc.example_vpc.id

  ingress {
    from_port   = 22
    to_port     = 22
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

# Create an EC2 instance
resource "aws_instance" "example_instance" {
  ami           = "ami-0c55b159cbfafe1f0" # Amazon Linux 2 AMI ID
  instance_type = "t2.micro"
  subnet_id     = aws_subnet.example_subnet.id
  security_groups = [aws_security_group.example_sg.name]

  tags = {
    Name = "ExampleInstance"
  }
}

Sample Terraform Code for Azure

Here’s a sample Terraform configuration to create a virtual machine in Azure:

# Provider configuration
provider "azurerm" {
  features {}
}

# Create a resource group
resource "azurerm_resource_group" "example_rg" {
  name     = "example-resources"
  location = "East US"
}

# Create a virtual network
resource "azurerm_virtual_network" "example_vnet" {
  name                = "example-vnet"
  address_space       = ["10.0.0.0/16"]
  location            = azurerm_resource_group.example_rg.location
  resource_group_name = azurerm_resource_group.example_rg.name
}

# Create a subnet
resource "azurerm_subnet" "example_subnet" {
  name                 = "example-subnet"
  resource_group_name  = azurerm_resource_group.example_rg.name
  virtual_network_name = azurerm_virtual_network.example_vnet.name
  address_prefixes     = ["10.0.1.0/24"]
}

# Create a network interface
resource "azurerm_network_interface" "example_nic" {
  name                = "example-nic"
  location            = azurerm_resource_group.example_rg.location
  resource_group_name = azurerm_resource_group.example_rg.name

  ip_configuration {
    name                          = "internal"
    subnet_id                     = azurerm_subnet.example_subnet.id
    private_ip_address_allocation = "Dynamic"
  }
}

# Create a virtual machine
resource "azurerm_virtual_machine" "example_vm" {
  name                  = "example-vm"
  location              = azurerm_resource_group.example_rg.location
  resource_group_name   = azurerm_resource_group.example_rg.name
  network_interface_ids = [azurerm_network_interface.example_nic.id]
  vm_size               = "Standard_DS1_v2"

  storage_image_reference {
    publisher = "Canonical"
    offer     = "UbuntuServer"
    sku       = "18.04-LTS"
    version   = "latest"
  }

  storage_os_disk {
    name              = "example-osdisk"
    caching           = "ReadWrite"
    create_option     = "FromImage"
    managed_disk_type = "Standard_LRS"
  }

  os_profile {
    computer_name  = "examplevm"
    admin_username = "adminuser"
    admin_password = "Password1234!"
  }

  os_profile_linux_config {
    disable_password_authentication = false
  }
}