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Formatting a Packer Template in HCL2

Packer allows us to create templates for generating cross-platform machine images, and HashiCorp provides its own configuration language for this task. In this lab, we'll test our HCL2 skills by fixing and otherwise neaten up an inaccurately written HCL2 Packer template. Just want to test your HCL2 reviewing skills? No Packer knowledge is needed to take this lab.

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Lab platform
Lab Info
Level
Beginner
Last updated
Aug 24, 2025
Duration
30m

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Table of Contents
  1. Challenge

    Fix Whitespace
    1. Open the provided template:

      cd packer
      
      vim ami-test.pkr.hcl
      
    2. To make viewing the template easier, let's neaten up the template by adjusting the tabs/whitespace:

      source "amazon-ebs" "ubuntu-ami-test": {
          access_key = "",
          secret_key = "",
          security_group_ids = [""],
          subnet_id = "",
          region = "us-east-1",
          ami_name = "ubuntu-ami-test_{{timestamp}}",
          instance_type = "t2.micro",
          source_ami = "ami-068663a3c619dd892",
          communicator = "ssh",
          ssh_username = "ubuntu"
      }
      
      build {
          sources = [ "source.amazon-ebs.ubuntu-ami-test" ]
      
          provisioner "shell" [
              script = "init.sh"
          ]
      }
      
  2. Challenge

    Adjust Structural Errors
    1. Update the template to remove the unnecessary colon (:) in the initial source block. The provisioner block also needs to be updated to work as an object not an array:

      source "amazon-ebs" "ubuntu-ami-test" {
          access_key = "",
          secret_key = "",
          security_group_ids = [""],
          subnet_id = "",
          region = "us-east-1",
          ami_name = "ubuntu-ami-test_{{timestamp}}",
          instance_type = "t2.micro",
          source_ami = "ami-068663a3c619dd892",
          communicator = "ssh",
          ssh_username = "ubuntu"
      }
      
      build {
          sources = [ "source.amazon-ebs.ubuntu-ami-test" ]
      
          provisioner "shell" {
              script = "init.sh"
          }
      }
      
    2. Finally, remove any commas:

      source "amazon-ebs" "ubuntu-ami-test" {
          access_key = ""
          secret_key = ""
          security_group_ids = [""]
          subnet_id = ""
          region = "us-east-1"
          ami_name = "ubuntu-ami-test_{{timestamp}}"
          instance_type = "t2.micro"
          source_ami = "ami-068663a3c619dd892"
          communicator = "ssh"
          ssh_username = "ubuntu"
      }
      
      build {
          sources = [ "source.amazon-ebs.ubuntu-ami-test" ]
      
          provisioner "shell" {
              script = "init.sh"
          }
      }
      
  3. Challenge

    Run the Build
    1. Using the credentials on the hands-on lab page, update the variables to use the provided access key, secret key, subnet ID, and security group.

    2. Save and exit the file.

    3. Run the build:

      packer build .
      
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