Change ubuntu hostname with Terraform. `terraform apply -target=null_resource.set-hostname`

set-hostname.tf

variable "server_ip" {
  default = "10.0.0.2"
}

variable "server_hostname" {
  default = "node01"
}

# Ubuntu reference for hostnamectl: http://manpages.ubuntu.com/manpages/trusty/man1/hostnamectl.1.html
resource "null_resource" "set-hostname" {
  connection {
    type = "ssh"
    user = "ubuntu"
    host = "${var.server_ip}"
  }

  provisioner "remote-exec" {
    inline = [
      "sudo hostnamectl set-hostname ${var.server_hostname}",
      "echo '127.0.0.1 ${var.server_hostname}' | sudo tee -a /etc/hosts",
      "sudo reboot"
    ]
  }
}

Another more elegant option: cloud-init passed on as user_data.

@miry Does this need a reboot?

thanks @miry. Your solution worked well except I had to change the order.
@paambaati a restart is not required. hostnamectl also sets local hostname. So it will reflect untill reboot. On reboot it will make it permanent.

  provisioner "remote-exec" {
    inline = [
      "echo '127.0.0.1 ${var.server_hostname}' | sudo tee -a /etc/hosts",
      "sudo hostnamectl set-hostname ${var.server_hostname}",
    ]
  }

I followed the same but it is not working

Code:

resource "null_resource" "setup-httpd" {

connection {

type = "ssh"

	host = "${file("../ec2-instance/host_ip.txt")}"

	user = "ec2-user"

	private_key = "${file("../ec2-instance/aws_ssh_key")}"

	timeout = "30s"

}

provisioner "remote-exec" {

	inline = [

	"sudo yum install -y httpd mod_ssl"

	]

}

}

How to change hostname if security group limit IPs that can connect to instance?