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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.

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Labs

Path Info

Level
Clock icon Beginner
Duration
Clock icon 30m
Published
Clock icon Oct 02, 2020

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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
      

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