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Aisalkyn Aidarova
Aisalkyn Aidarova

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Terraform Provisioners

#aws #terraform #devops #tutorial

🎯 Lab Goal

You will:

  • Create an EC2 instance
  • Install NGINX using remote-exec
  • Save EC2 IP locally using local-exec
  • Upload a file using file provisioner
  • Verify everything in browser

🧱 STEP 1 — Prerequisites (VERY IMPORTANT)

✅ You must have:

  • AWS account
  • Terraform installed

  • Key pair created in AWS:

    • Name: terraform-key
    • Download: terraform-key.pem

✅ Place file in your project: 

provisioner-lab/
  main.tf
  terraform-key.pem
  index.html
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🧱 STEP 2 — Fix Key Permissions (Mac/Linux) 

chmod 400 terraform-key.pem
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❗ If you skip → SSH WILL FAIL

🧱 STEP 3 — Create index.html (file provisioner test)

📄 index.html

<h1>Welcome from Terraform Provisioner Lab</h1>
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🧱 STEP 4 — Security Group (AWS Console)

Allow:

Type Port Source
SSH 22 0.0.0.0/0
HTTP 80 0.0.0.0/0

Copy Security Group ID:

sg-xxxxxxxx
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🧱 STEP 5 — Full Terraform Code

📄 main.tf

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "web" {
  ami           = "ami-0c02fb55956c7d316" # Amazon Linux 2
  instance_type = "t2.micro"

  key_name = "terraform-key"

  vpc_security_group_ids = ["sg-xxxxxxxx"] # replace

  # ✅ FILE PROVISIONER (upload HTML)
  provisioner "file" {
    source      = "index.html"
    destination = "/home/ec2-user/index.html"

    connection {
      type        = "ssh"
      user        = "ec2-user"
      private_key = file("terraform-key.pem")
      host        = self.public_ip
    }
  }

  # ✅ REMOTE-EXEC (install nginx + deploy page)
  provisioner "remote-exec" {
    inline = [
      "sudo yum install nginx -y",
      "sudo systemctl start nginx",
      "sudo systemctl enable nginx",
      "sudo mv /home/ec2-user/index.html /usr/share/nginx/html/index.html"
    ]

    connection {
      type        = "ssh"
      user        = "ec2-user"
      private_key = file("terraform-key.pem")
      host        = self.public_ip
    }
  }

  # ✅ LOCAL-EXEC (save IP locally)
  provisioner "local-exec" {
    command = "echo ${self.public_ip} > public_ip.txt"
  }

  tags = {
    Name = "provisioner-lab"
  }
}
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🧪 STEP 6 — Run Terraform 

terraform init
terraform apply -auto-approve
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⚙️ WHAT HAPPENS INTERNALLY

  1. EC2 instance created
  2. Terraform connects via SSH
  3. File provisioner uploads HTML
  4. Remote-exec installs nginx
  5. HTML moved to nginx folder
  6. local-exec saves IP to file

🔍 STEP 7 — VERIFY

✅ Check local file 

cat public_ip.txt
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Example:

3.145.23.10
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✅ Open browser 

http://<EC2_PUBLIC_IP>
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👉 You should see:

Welcome from Terraform Provisioner Lab
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🧪 STEP 8 — TEST & BREAK (IMPORTANT FOR INTERVIEW)

❌ Test 1: Wrong key

Change:

private_key = file("wrong.pem")
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👉 Result:

  • SSH fails
  • Provisioning fails

❌ Test 2: Remove port 22

👉 Result:

  • Terraform hangs (waiting SSH)

❌ Test 3: Remove sudo

👉 Result:

  • Permission denied
  • NGINX not installed

🔁 STEP 9 — DESTROY 

terraform destroy -auto-approve
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🧠 WHAT YOU LEARNED

Provisioners:

  • file → copy file
  • remote-exec → configure server
  • local-exec → run locally

Execution order:

  1. Create EC2
  2. file provisioner
  3. remote-exec
  4. local-exec

Key concepts:

  • self.public_ip
  • SSH connection block
  • Key permissions
  • Provisioner dependency on resource

🎯 REAL DEVOPS TIP (IMPORTANT)

👉 In production, replace this with:

  • user_data (bootstrap)
  • Ansible (config)
  • Packer (pre-built AMI)

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