Featured resource
2025 Tech Upskilling Playbook
Tech Upskilling Playbook

Build future-ready tech teams and hit key business milestones with seven proven plays from industry leaders.

Check it out
  • Lab
    • Libraries: If you want this lab, consider one of these libraries.
    • Cloud
Google Cloud Platform icon
Labs

Formatting a Packer Template in JSON

Packer allows us to create templates for generating cross-platform machine images — templates that can be written in JSON. In this lab, we'll test our JSON skills by fixing and otherwise neatening up an inaccurately written JSON Packer template. Just want to test your JSON reviewing skills? No Packer knowledge is needed to take this lab.

Google Cloud Platform icon
Lab platform
Lab Info
Level
Beginner
Last updated
Apr 06, 2025
Duration
30m

Contact sales

By filling out this form and clicking submit, you acknowledge our privacy policy.
Table of Contents
  1. Challenge

    Fix Whitespace
    1. Open the provided template:

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

      {
          "variables": {
              "aws_access_key": "",
              "aws_secret_key": "",
              "aws_subnet_id": ""
          }
          "builders": {
              {
                  "type": "amazon-ebs",
                  "access_key": "{{user `aws_access_key`}}",
                  "secret_key": "{{user `aws_secret_key`}}",
                  "region": "us-east-1",
                  "subnet_id": "{{user `aws_subnet_id`}}",
                  "source_ami_filter": {
                      "filters": {
                          "virtualization-type": "hvm",
                          "name": "ubuntu/images/*ubuntu-focal-20.04-amd64-server-*",
                          "root-device-type": "ebs"
                      },
                      "owners": ["099720109477"],
                      "most_recent": true
                  },
                  "security_group_filter": {
                      "filters": {
                          "tag:Class": "packer"
                      }
                  }
                  "instance_type": "t2.micro",
                  "ssh_username": "ubuntu",
                  "ami_name": "ubuntu-ami-test_{{timestamp}}"
              }
          }
          "provisioners": {
              {
                  "type": "shell",
                  "script": "./init.sh"
              }
          }
      }
      
  2. Challenge

    Adjust Structural Errors
    1. The provided template has builders and provisioners provided as objects when they should be arrays. Switch the brackets for these overall components:

      {
          "variables": {
              "aws_access_key": "",
              "aws_secret_key": "",
              "aws_subnet_id": ""
          }
          "builders": [
              {
                  "type": "amazon-ebs",
                  "access_key": "{{user `aws_access_key`}}",
                  "secret_key": "{{user `aws_secret_key`}}",
                  "region": "us-east-1",
                  "subnet_id": "{{user `aws_subnet_id`}}",
                  "source_ami_filter": {
                      "filters": {
                          "virtualization-type": "hvm",
                          "name": "ubuntu/images/*ubuntu-focal-20.04-amd64-server-*",
                          "root-device-type": "ebs"
                      },
                      "owners": ["099720109477"],
                      "most_recent": true
                  },
                  "security_group_filter": {
                      "filters": {
                          "tag:Class": "packer"
                      }
                  }
                  "instance_type": "t2.micro",
                  "ssh_username": "ubuntu",
                  "ami_name": "ubuntu-ami-test_{{timestamp}}"
              }
          ]
          "provisioners": [
              {
                  "type": "shell",
                  "script": "./init.sh"
              }
          ]
      }
      
    2. Finally, fix any missing commas:

      {
          "variables": {
              "aws_access_key": "",
              "aws_secret_key": "",
              "aws_subnet_id": ""
          },
          "builders": [
              {
                  "type": "amazon-ebs",
                  "access_key": "{{user `aws_access_key`}}",
                  "secret_key": "{{user `aws_secret_key`}}",
                  "region": "us-east-1",
                  "subnet_id": "{{user `aws_subnet_id`}}",
                  "source_ami_filter": {
                      "filters": {
                          "virtualization-type": "hvm",
                          "name": "ubuntu/images/*ubuntu-focal-20.04-amd64-server-*",
                          "root-device-type": "ebs"
                      },
                      "owners": ["099720109477"],
                      "most_recent": true
                  },
                  "security_group_filter": {
                      "filters": {
                          "tag:Class": "packer"
                      }
                  },
                  "instance_type": "t2.micro",
                  "ssh_username": "ubuntu",
                  "ami_name": "ubuntu-ami-test_{{timestamp}}"
              }
          ],
          "provisioners": [
              {
                  "type": "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, and subnet ID.

    2. Save and exit the file.

    3. Validate the template:

      packer validate ami-test.json
      
    4. Run the build:

      packer build ami-test.json
      
About the author

Pluralsight Skills gives leaders confidence they have the skills needed to execute technology strategy. Technology teams can benchmark expertise across roles, speed up release cycles and build reliable, secure products. By leveraging our expert content, skill assessments and one-of-a-kind analytics, keep up with the pace of change, put the right people on the right projects and boost productivity. It's the most effective path to developing tech skills at scale.

Real skill practice before real-world application

Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.

Learn by doing

Engage hands-on with the tools and technologies you’re learning. You pick the skill, we provide the credentials and environment.

Follow your guide

All labs have detailed instructions and objectives, guiding you through the learning process and ensuring you understand every step.

Turn time into mastery

On average, you retain 75% more of your learning if you take time to practice. Hands-on labs set you up for success to make those skills stick.

Get started with Pluralsight