为什么 terraform aws 代码无法呈现？

Question

Terraform version = 0.12

resource "aws_instance" "bespin-ec2-web" {
  ami = "ami-0bea7fd38fabe821a"
  instance_type = "t2.micro"
  vpc_security_group_ids = [aws_security_group.bespin-sg.id]
  subnet_id = aws_subnet.bespin-subnet-public-a.id
  associate_public_ip_address = true
  tags = {
    Name = "bespin-ec2-web-a"
  }
  user_data = data.template_file.user_data.rendered
}

data "template_file" "user_data" {
template = file("${path.module}/userdata.sh")
}

userdata.sh file

 #!/bin/bash
   USERS="bespin"
   GROUP="bespin"
   for i in $USERS; do
   /usr/sbin/adduser ${i};
   /bin/echo ${i}:${i}1! | chpasswd;
   done

   cp -a /etc/ssh/sshd_config /etc/ssh/sshd_config_old
   sed -i 's/PasswordAuthentication no/#PasswordAuthentication no/' /etc/ssh/sshd_config
   sed -i 's/#PasswordAuthentication yes/PasswordAuthentication yes/' /etc/ssh/sshd_config
   systemctl restart sshd

terraform plan result

Error: failed to render : <template_file>:5,24-25: Unknown variable; There is no variable named "i"., and 2 other di
agnostic(s)

  on instance.tf line 13, in data "template_file" "user_data":
  13: data "template_file" "user_data" {

Why am I getting an error?

Answer 1

The template argument in the template_file data source is processed as Terraform template syntax.

In this syntax, using ${...} has a special meaning, that the ... part will be injected by some var that is passed into the template.

Bash also allows this syntax, for getting the values of variables as your intending to use it.

To reconcile this, you'll need to escape the $ character so that the terraform template compiler will leave it be, which you can do by doubling up the character: $${i} in all cases.

https://www.terraform.io/docs/configuration/expressions.html#string-templates