- Lab
-
Libraries: If you want this lab, consider one of these libraries.
- Cloud

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.

Lab Info
Table of Contents
-
Challenge
Fix Whitespace
-
Open the provided template:
cd packer
vim ami-test.json
-
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" } } }
-
-
Challenge
Adjust Structural Errors
-
The provided template has
builders
andprovisioners
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" } ] }
-
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" } ] }
-
-
Challenge
Run the Build
-
Using the credentials on the hands-on lab page, update the variables to use the provided access key, secret key, and subnet ID.
-
Save and exit the file.
-
Validate the template:
packer validate ami-test.json
-
Run the build:
packer build ami-test.json
-
About the author
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.