Terraform cycle error with AWS EC2 instance, volume and template file

it flag

Could you please help to explain and work around this error?

I have the following TF program for an instance with an EBS volume and template file using that volume id:

resource "aws_instance" "edge1" {

  instance_type = "t3a.micro" 

  ami =
  key_name = "ozonm"

  £ root block device 
  root_block_device {
    volume_size = 10

  user_data = data.template_file.user_data_edge1.rendered

£ End of resource "aws_instance" "edge1" 

£ EBS for homes
resource "aws_ebs_volume" "homes" {
  availability_zone = aws_instance.edge1.availability_zone
  size = 1

resource "aws_volume_attachment" "homes-volume-attachment" {
  device_name = "/dev/xvdf"
  instance_id =
  volume_id   =

data "template_file" "user_data_edge1" {  
  template = file("metadata-edge1.yml", { vol_id = })

So this gives me a cycle error:

 Error: Cycle: data.template_file.user_data_edge1, aws_instance.edge1,

while I think it should not. I know what circular dependence is, when first objects refers to the second, while the second refers to the first. But I think it's totally fine in this case with the following order:

  • volume is created
  • template file is rendered using the volume id
  • instance is created with the template file for user_data
  • volume is attached to the instance

But the TF graph shows that the instance depends on the volume:

TF graph

So, why is this happening, and how can I use a volume id in the template file for the instance?

Thanks in advance!

jp flag
Probably cycle is due to use of `aws_instance.edge1.availability_zone` in `` definition .
Artem Trunov avatar
it flag
None, it didn't matter when I tried.
it flag

Ok, so after some experiments, I found that the solution is to use depends_on meta-argument.

resource "aws_instance" "edge1" {

 depends_on [

In this case also availability_zone in must not refer back to the instance.

Also, use of data for making a template is not necessary, one can place template right into the body of aws_instance resource definition:

user_data = templatefile(...)

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