What is Terraform Provisioners?

Question

Accepted Answer

**Provisioners** — execute actions on resources during create/delete.

```hcl
resource "aws_instance" "web" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  key_name      = aws_key_pair.deployer.key_name

# File provisioner
  provisioner "file" {
    source      = "scripts/deploy.sh"
    destination = "/tmp/deploy.sh"

connection {
      type        = "ssh"
      host        = self.public_ip
      user        = "ubuntu"
      private_key = file("~/.ssh/id_rsa")
    }
  }

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

# Local-exec provisioner
  provisioner "local-exec" {
    command = "ansible-playbook -i ${self.public_ip}, provision.yml"
    environment = {
      ANSIBLE_HOST_KEY_CHECKING = "False"
    }
  }

# Destroy provisioner
  provisioner "local-exec" {
    when    = destroy
    command = "echo 'Instance ${self.id} destroyed' >> destroy.log"
  }
}
```

**Types:**
- file: copy files to/from resource.
- local-exec: run local command.
- remote-exec: run remote command.

**Best Practices:**
- Prefer user_data/scripts over provisioners.
- Use only when no other option exists.
- Handle failures gracefully.

DevOps: What is Terraform Provisioners?