Packer HCL Environment Variables

Converting Packer templates from json to HCL for Packer version 1.7.2. The easiest thing to do is try the automated conversion:

packer hcl2_upgrade -output-file=template-converted.pkr.hcl template.json

For environment variables we need to set them with a PKR_VAR prefix e.g.

export PKR_VAR_IAM_ROLE=jonny-test

Then that can be defined in the template.pkr.hcl file with:

variable "iam_role" {
  type    = string
  default = "${env("IAM_ROLE")}"
  validation {
    condition     = length(var.iam_role) > 0
    error_message = <<EOF
The IAM_ROLE environment variable must be set.
EOF
  }
}

And then used in later sections like this:

source "amazon-ebs" "debian" {
  ami_name = "my-debian-10-{{isotime `2006-01-02 15-04-05`}}"
  assume_role {
    role_arn     = "${var.iam_role}"
    session_name = "packer"
  }

Then your validation should work:

packer validate  template.pkr.hcl

And if you want to check the variables available when using the template:

packer console template.pkr.hcl 

and at the prompt enter:

variables