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.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

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"
        }
    }
}

Adjust Structural Errors

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"
        }
    ]
}

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"
        }
    ]
}

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
```

What are Hands-on Labs

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.

Formatting a Packer Template in JSON

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