# Exercise: Implementing Provisioners and Functions

# Objective

In this exercise, participants will:

• Implement provisioners to install a web server (Nginx) on an Azure Virtual Machine.
• Use Terraform functions to dynamically adjust the configuration based on the environment.
• Create and use separate workspaces for development (dev) and production (prod) environments.

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# Steps

# Step 1: Provision a Virtual Machine with Nginx Using a Provisioner

1. Define a Virtual Machine in main.tf:

   • In your project directory, create or open a main.tf file.

   • Add a resource block for an Azure Virtual Machine, configuring basic settings:

     resource "azurerm_virtual_machine" "example" {
       name                  = "example-vm"
       location              = var.location
       resource_group_name   = var.resource_group_name
       network_interface_ids = [azurerm_network_interface.example.id]
       vm_size               = var.vm_size
     
       storage_image_reference {
         publisher = "Canonical"
         offer     = "UbuntuServer"
         sku       = "18.04-LTS"
         version   = "latest"
       }
     
       os_profile {
         computer_name  = "examplevm"
         admin_username = "adminuser"
         admin_password = "P@ssw0rd123!"
       }
     
       os_profile_linux_config {
         disable_password_authentication = false
       }
     
       # Provisioner to install Nginx on the VM
       provisioner "remote-exec" {
         connection {
           type        = "ssh"
           host        = self.public_ip_address
           user        = "adminuser"
           password    = "P@ssw0rd123!"
         }
     
         inline = [
           "sudo apt-get update",
           "sudo apt-get install -y nginx"
         ]
       }
     }

   • This configuration defines a Linux VM running Ubuntu Server 18.04 with an inline remote-exec provisioner to install Nginx after the VM is provisioned.

2. Define Network Interface and Public IP (if needed):

   • Ensure the VM has a network interface and public IP so the provisioner can connect and install Nginx.
   • Example:

     resource "azurerm_network_interface" "example" {
       name                = "example-nic"
       location            = var.location
       resource_group_name = var.resource_group_name
     
       ip_configuration {
         name                          = "internal"
         subnet_id                     = azurerm_subnet.example.id
         private_ip_address_allocation = "Dynamic"
         public_ip_address_id          = azurerm_public_ip.example.id
       }
     }
     
     resource "azurerm_public_ip" "example" {
       name                = "example-pip"
       location            = var.location
       resource_group_name = var.resource_group_name
       allocation_method   = "Static"
     }

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# Step 2: Use Terraform Functions to Adjust Configuration Dynamically

1. Define the VM Size Based on Environment:

   • Use the terraform.workspace variable and a conditional expression to set the VM size.
   • Add the following code to variables.tf or directly in main.tf:

     variable "vm_size" {
       description = "The size of the VM based on the environment"
       type        = string
       default     = terraform.workspace == "prod" ? "Standard_DS2_v2" : "Standard_DS1_v2"
     }

2. Use the length() Function (Optional Example):

   • To dynamically calculate values based on lists, you could use the length() function in expressions:

     output "number_of_nics" {
       description = "The number of network interfaces"
       value       = length(azurerm_network_interface.example)
     }

   • This example calculates the number of network interfaces attached to the VM.

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# Step 3: Switch Workspaces for Dev and Prod Environments

1. Create and Switch to the Development Workspace:

   • In the terminal, run:

     terraform workspace new dev

   • Terraform will create a new workspace called dev and switch to it.

2. Create the Production Workspace:

   • Create another workspace for the production environment:

     terraform workspace new prod

3. Verify Workspace:

   • You can check your current workspace with:

     terraform workspace show

4. Set Environment-Specific Values (Optional):

   • Use separate variable files (e.g., dev.tfvars and prod.tfvars) to provide different values for location or resource_group_name based on the workspace.

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# Step 4: Run terraform plan and terraform apply to Verify the Setup

1. Initialize the Project (if not already initialized):

   • Run terraform init to download necessary provider plugins and prepare the environment:

     terraform init

2. Run terraform plan:

   • In the current workspace, run terraform plan to verify the configuration:

     terraform plan -var-file="dev.tfvars"  # for dev
     terraform plan -var-file="prod.tfvars" # for prod

   • Review the output to ensure Terraform will provision a VM with the correct configurations (e.g., VM size based on the workspace).

3. Run terraform apply to Deploy the VM:

   • Run terraform apply to create the VM and install Nginx via the provisioner:

     terraform apply -var-file="dev.tfvars"  # for dev
     terraform apply -var-file="prod.tfvars" # for prod

   • Type yes when prompted to confirm the apply operation.

4. Verify the Setup in the Azure Portal:

   • Go to the Azure Portal and check that the VM has been created in the correct environment with Nginx installed.

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# Verification

• Confirm VM Creation:

  • Verify that a VM has been created in Azure for each workspace and is using the correct VM size based on the environment.

• Verify Nginx Installation:

  • Use SSH to connect to the VM and check if Nginx is running:

    ssh adminuser@<VM_PUBLIC_IP>
    sudo systemctl status nginx

• Verify Output Values (if configured):

  • Check any outputs, such as number_of_nics, to ensure they reflect the actual setup.

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