Why provisioners are a last resort in Terraform - See It in Action

Why Provisioners Are a Last Resort in Terraform

📖 Scenario: You are managing cloud infrastructure using Terraform. You want to understand how to handle tasks that Terraform does not natively support, like running scripts on a virtual machine after it is created.

🎯 Goal: Build a simple Terraform configuration that creates a virtual machine and uses a provisioner as a last resort to run a script on it.

📋 What You'll Learn

Create a Terraform resource for a virtual machine

Add a connection block to enable communication with the VM

Add a provisioner block to run a script on the VM

Understand why provisioners should be avoided when possible

💡 Why This Matters

🌍 Real World

Provisioners are sometimes needed to perform tasks that Terraform cannot do natively, like installing software or configuring a VM after creation.

💼 Career

Cloud engineers and DevOps professionals often need to understand when and how to use provisioners safely to avoid unstable infrastructure deployments.

1

Create a Terraform resource for a virtual machine

Write a Terraform resource block called aws_instance named example with the ami set to "ami-0c55b159cbfafe1f0" and instance_type set to "t2.micro".

Terraform

# Your code here to create aws_instance example with specified ami and instance_type

Need a hint?

Use the resource keyword with aws_instance and specify the ami and instance_type exactly as given.

2

Add a connection block to enable communication with the VM

Add a connection block inside the aws_instance.example resource with type set to "ssh", user set to "ec2-user", and private_key set to file("~/.ssh/id_rsa").

Terraform

resource "aws_instance" "example" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"

  # Add connection block here
}

Need a hint?

The connection block tells Terraform how to connect to the VM for running commands.

3

Add a provisioner block to run a script on the VM

Inside the aws_instance.example resource, add a provisioner block of type remote-exec that runs the command "echo Hello, Terraform! > /tmp/hello.txt".

Terraform

resource "aws_instance" "example" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"

  connection {
    type        = "ssh"
    user        = "ec2-user"
    private_key = file("~/.ssh/id_rsa")
  }

  # Add provisioner block here
}

Need a hint?

The provisioner runs commands on the VM after it is created. Use remote-exec with an inline command.

4

Add a comment explaining why provisioners are a last resort

Add a comment at the top of the Terraform file explaining: "Provisioners are a last resort because they can cause unpredictable failures and make infrastructure harder to manage."

Terraform

# Your comment here explaining why provisioners are a last resort
resource "aws_instance" "example" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"

  connection {
    type        = "ssh"
    user        = "ec2-user"
    private_key = file("~/.ssh/id_rsa")
  }

  provisioner "remote-exec" {
    inline = ["echo Hello, Terraform! > /tmp/hello.txt"]
  }
}

Need a hint?

Write a clear comment at the top of the file explaining the risks of using provisioners.