"Invalid function argument" with Userdata in Terraform - amazon-web-services

Question

I'm trying to pass user data over a file so the code will look less clumsy, but having trouble. I've tried all the different combinations but nothing is working.
I went through the Terraform documentation, it doesn't give any special instructions for the path value.
Folder structure:
project1/env/dr/compute/main.tf
module "share_server" {
count = 2
source = "../../../../terraform_modules/modules/compute/"
ami = data.aws_ami.amazonlinux2.id
instance_type = "t3.micro"
availability_zone = data.aws_availability_zones.az.names[count.index]
subnet_id = data.aws_subnets.app_subnet.ids[count.index]
associate_public_ip_address = "false"
key_name = "app7"
vpc_security_group_ids = ["sg-08d38198dc153c410"]
instance_root_device_size = 20
kms_key_id = "ea88e727-e506-4530-b92f-2827d8f9c94e"
volume_type = "gp3"
platform = "linux"
backup = true
Environment = "dr"
server_role = "Application_Server"
server_component = "share_servers"
hostname = "app-dr-test-10"
tags = {
Name = "${local.instance_name}-share-${count.index}"
}
}
My ec2 module resides in the below folder structure.
project1/modules/compute/ec2.tf
project1/modules/computer/userdata/share_userdata.tpl
The ec2.tf code is below. I have removed the bottom half of the code so the post won't be too big to read.
resource "aws_instance" "ec2" {
ami = var.ami
instance_type = var.instance_type
availability_zone = var.availability_zone
subnet_id = var.subnet_id
associate_public_ip_address = var.associate_public_ip_address
user_data = templatefile("userdata/share_userdata.tpl",
{ hostname = var.hostname }
)
Error:
PS B:\PubOps\app7_terraform\environments\dr\compute> terraform apply
│ Error: Invalid function argument │
│ on ..\..\..\..\terraform_modules\modules\compute\main.tf line 10, in resource "aws_instance" "ec2":
│
10: user_data = templatefile("userdata/share_userdata.tpl",
│ 11: {
│ 12: hostname = var.hostname
│ 13: })
│
│ Invalid value for "path" parameter: no file exists at userdata/share_userdata.tpl; this function works only with files that are distributed as part of the
│ configuration source code, so if this file will be created by a resource in this configuration you must instead obtain this result from an attribute of that
│ resource. ╵ PS B:\PubOps\alfresco7_terraform\environments\dr\compute>
User data
#!/bin/bash
yum update -y
### hostname
sudo hostnamectl set-hostname $hostname
echo "127.0.0.1 $hostname
$hostname localhost4 localhost4.localdomain4" > /etc/hosts
echo "preserve_hostname: true" >> /etc/cloud/cloud.cfg
#EFS utility and mounting
yum install -y amazon-efs-utils
EOF
References:
The same code mentioned on GitHub, maybe it is working for the author, but not for me: https://github.com/kunduso/ec2-userdata-terraform/blob/add-userdata/ec2.tf
My goal is to set up user data and pass variables over the AWS parameter store as shown in the below URL, but I couldn't pass the basic setup.
https://skundunotes.com/2021/11/17/manage-sensitive-variables-in-aws-ec2-user-data-with-terraform/
I tried pointing the file like this: ./share_userdata.tpl.
I tried with absolute path b/project1/dr/compute/share_userdata.tpl.
I also tried giving $module.path/share_userdata.tpl.
None of them worked.

Answer 1

The error is rather clear:
no file exists at userdata/share_userdata.tpl
Thus you must ensure that in the folder where you execute templatefile("userdata/share_userdata.tpl" there is a subfolder called userdata and in that folder there is a file share_userdata.tpl.

Answer 2

You need to pass the full or relative path in your template file. You can try the below code for relative path e.g.:
resource "aws_instance" "ec2" {
ami = var.ami
instance_type = var.instance_type
availability_zone = var.availability_zone
subnet_id = var.subnet_id
associate_public_ip_address = var.associate_public_ip_address
user_data = templatefile("./userdata/share_userdata.tpl",
{ hostname = var.hostname }
)
Here ./ indicating current folder.
Assuming the ec2.tf and userdata folder exist in same path. for example: project1/modules/compute/.