353.2 Packer (weight: 2)

Tech Tutorial: 353.2 Packer (weight: 2) #

Introduction #

In this tutorial, we will delve into using Packer, a powerful open-source tool designed for creating identical machine images for multiple platforms from a single source configuration. Packer is widely used in infrastructure as code environments, facilitating continuous delivery and versioning of images. It can automate the creation of various machine image formats for platforms like AWS EC2, VMware, Docker, and more.

Exam Objective: #

  • Understand and use Packer for automating machine image creation.

Key Knowledge Areas: #

  • Packer installation and configuration
  • Writing Packer templates
  • Building images
  • Provisioners and post-processors

Utilities: #

  • packer

Step-by-Step Guide #

Step 1: Installing Packer #

Packer is easy to install. You can download a precompiled binary from its official website or use a package manager. For Linux systems:

wget https://releases.hashicorp.com/packer/1.7.8/packer_1.7.8_linux_amd64.zip
unzip packer_1.7.8_linux_amd64.zip
sudo mv packer /usr/local/bin

Verify the installation by checking the version:

packer version

Step 2: Writing Your First Packer Template #

Packer uses JSON or HCL2 (HashiCorp Configuration Language) for its template. Here, we’ll use JSON for simplicity. Create a file named example.json:

{
  "builders": [
    {
      "type": "docker",
      "image": "ubuntu",
      "commit": true
    }
  ],
  "provisioners": [
    {
      "type": "shell",
      "inline": [
        "apt-get update",
        "apt-get install -y nginx"
      ]
    }
  ]
}

This basic template defines a single builder (Docker) and a provisioner that installs Nginx on an Ubuntu image.

Step 3: Building an Image with Packer #

To build the image as defined in your template, run:

packer build example.json

Packer will execute the defined steps, creating a Docker container, running the provisioner scripts, and committing the changes to form a new Docker image.

Step 4: Advanced Configuration #

Let’s explore a more advanced template that builds an AWS AMI:

{
  "builders": [
    {
      "type": "amazon-ebs",
      "access_key": "YOUR_ACCESS_KEY_HERE",
      "secret_key": "YOUR_SECRET_KEY_HERE",
      "region": "us-east-1",
      "source_ami": "ami-0c55b159cbfafe1f0",
      "instance_type": "t2.micro",
      "ssh_username": "ubuntu",
      "ami_name": "packer-example {{timestamp}}"
    }
  ],
  "provisioners": [
    {
      "type": "shell",
      "inline": [
        "sudo apt-get update",
        "sudo apt-get install -y apache2"
      ]
    }
  ]
}

This configuration will create a new AWS AMI with Apache installed.

Detailed Code Examples #

Example: Provisioners #

Packer supports multiple types of provisioners. Here’s an example using a file provisioner to copy files to the image:

"provisioners": [
  {
    "type": "file",
    "source": "./mywebsite",
    "destination": "/var/www/html"
  },
  {
    "type": "shell",
    "inline": [
      "systemctl restart apache2"
    ]
  }
]

Example: Post-Processors #

Post-processors are used to process images after they are built. For instance, compressing an output artifact:

"post-processors": [
  {
    "type": "compress",
    "output": "build/{{.BuildName}}.tar.gz",
    "compression_level": 9,
    "keep_input_artifact": true
  }
]

Conclusion #

Packer is an incredibly powerful tool for automating the creation of machine images across multiple platforms. By understanding the basics of its configuration and operation, as demonstrated in this tutorial, you can integrate Packer into your infrastructure to ensure consistency, repeatability, and automation in your deployments. Whether you’re working with cloud providers like AWS or virtualization platforms like VMware, Packer streamlines the process of image creation and management, making it an essential tool in modern DevOps practices.