Remote-exec provisioner in Terraform - Step-by-Step Execution

Process Flow - Remote-exec provisioner

Terraform starts apply

↓

Create resource (e.g., VM)

↓

Wait for resource to be ready

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Run remote-exec provisioner

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Connect via SSH or WinRM

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Execute commands on remote machine

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Provisioning complete

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Terraform apply finishes

Terraform creates the resource, then connects remotely to run commands on it using SSH or WinRM, completing provisioning.

Execution Sample

Terraform

resource "aws_instance" "example" {
  ami                         = "ami-12345678"
  instance_type               = "t2.micro"
  associate_public_ip_address = true
  key_name                    = "example-key"

  provisioner "remote-exec" {
    connection {
      type        = "ssh"
      user        = "ubuntu"
      host        = self.public_ip
      private_key = file("~/.ssh/mykey.pem")
    }
    inline = ["sudo apt-get update", "sudo apt-get install -y nginx"]
  }
}

This code creates an AWS instance and runs commands remotely to update packages and install nginx.

Process Table

Step	Action	Resource State	Provisioner Connection	Commands Executed	Result
1	Start terraform apply	No resource	No connection	No commands	Begin process
2	Create aws_instance	Instance launching	No connection	No commands	Instance created but not ready
3	Wait for instance ready	Instance running	No connection	No commands	Instance ready for connection
4	Connect via SSH	Instance running	SSH connected	No commands	Connection established
5	Run command: sudo apt-get update	Instance running	SSH connected	sudo apt-get update	Command success
6	Run command: sudo apt-get install -y nginx	Instance running	SSH connected	sudo apt-get install -y nginx	Command success
7	Provisioning complete	Instance running	SSH disconnected	All commands done	Provisioning finished
8	Terraform apply complete	Instance running	No connection	No commands	Apply finished successfully

💡 All commands executed successfully, provisioning finished, terraform apply completes.

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 7	Final
Resource State	No resource	Instance launching	Instance running	Instance running	Instance running	Instance running
Provisioner Connection	No connection	No connection	No connection	SSH connected	SSH disconnected	No connection
Commands Executed	None	None	None	None	Update, Install nginx	All commands done

Key Moments - 3 Insights

Why does terraform wait before running remote-exec commands?

Terraform waits until the instance is fully running and accessible (see Step 3) before connecting via SSH (Step 4) to avoid connection failures.

What happens if the remote-exec commands fail?

If commands fail, terraform apply stops and reports an error at the provisioner step (between Steps 5-6), preventing incomplete provisioning.

Does remote-exec run before or after resource creation?

Remote-exec runs only after the resource is created and ready (after Step 3), as shown by connection established in Step 4.

Visual Quiz - 3 Questions

Look at the execution table, at which step does terraform establish SSH connection?

A Step 4

B Step 2

C Step 6

D Step 8

💡 Hint

Check the 'Provisioner Connection' column for when it changes to 'SSH connected'.

At which step does terraform finish running all remote commands?

A Step 5

B Step 7

C Step 6

D Step 8

💡 Hint

Look for 'Commands Executed' column showing all commands done.

If the instance was not ready, what would happen to the connection step?

A Connection would succeed immediately

B Terraform would skip remote-exec

C Terraform would wait until instance is ready before connecting

D Terraform would fail apply instantly

💡 Hint

Refer to Step 3 and Step 4 showing waiting and then connection.

Concept Snapshot

Terraform Remote-exec provisioner:
- Runs commands on a remote resource after creation
- Connects via SSH (Linux) or WinRM (Windows)
- Waits for resource readiness before connecting
- Executes inline or script commands
- Fails apply if commands fail
- Used for initial setup/configuration

Full Transcript

Terraform Remote-exec provisioner works by first creating the resource, such as a virtual machine. Terraform waits until the resource is fully running and accessible. Then it connects remotely using SSH or WinRM. After connection, it runs the specified commands on the remote machine. These commands can update software or install packages. If any command fails, terraform stops and reports an error. Once all commands succeed, provisioning is complete and terraform finishes the apply process.