Day 19 - Understanding Terraform Provisioners with AWS EC2 and Nginx

Introduction

For Day 19 of my challenge, I explored Terraform Provisioners using AWS EC2.

In this demo, I used:

• local-exec
• file provisioner
• remote-exec

The goal was to:

• Deploy an EC2 instance
• Copy a shell script into the server
• Install nginx automatically
• Validate the deployment from the browser

This exercise also helped me understand why HashiCorp considers provisioners a “last resort” approach in production environments.

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Architecture Diagram

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Types of Terraform Provisioners

local-exec

provisioner "local-exec" {
  command = "echo ${self.public_ip} >> inventory.txt"
}

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file Provisioner

provisioner "file" {
  source      = "welcome.sh"
  destination = "/tmp/welcome.sh"
}

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remote-exec

provisioner "remote-exec" {
  inline = [
    "chmod +x /tmp/welcome.sh",
    "sudo /tmp/welcome.sh"
  ]
}

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Terraform Deployment

Initialize Terraform

terraform init

Validate Terraform Configuration

terraform validate

Review Terraform Plan

terraform plan

Deploy Infrastructure

terraform apply

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Validation Steps

Validate local-exec

cat inventory.txt

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Validate file Provisioner

ls -l /tmp/welcome.sh

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Validate remote-exec

sudo systemctl status nginx

curl localhost

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Browser Validation

Open:

http://54.82.86.210/

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Why Provisioners Are Considered Last Resort

Terraform is designed mainly for infrastructure provisioning.

Provisioners introduce procedural execution into a declarative infrastructure workflow, which can create:

• SSH dependency failures
• Timing issues
• Non-idempotent behavior
• Harder troubleshooting
• More fragile automation

Because of this, HashiCorp recommends alternatives such as:

• user_data
• cloud-init
• Packer
• AWS Systems Manager
• Ansible

This exercise helped me understand the practical difference between infrastructure provisioning and server configuration management.

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Key Learnings

• local-exec runs on the local machine
• file provisioner copies files into EC2
• remote-exec executes commands inside EC2 through SSH
• Provisioners execute during resource creation
• Provisioners do not rerun automatically after script changes
• SSH connectivity is critical for remote-exec and file provisioners
• Terraform is best suited for infrastructure provisioning
• user_data and cloud-init are usually better production approaches

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Cleanup

terraform destroy

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Conclusion

Day 19 provided practical experience with Terraform Provisioners using AWS EC2 and nginx.

I successfully automated:

• EC2 deployment
• Script transfer
• nginx installation
• Web server validation

More importantly, I learned why provisioners should be used carefully and why production environments usually prefer immutable infrastructure and dedicated configuration management tools.

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Video Reference

Jay