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Packer

Introduction​

This cheat sheet provides a quick reference for some common Packer commands and concepts. Packer is an open-source tool for automating the creation of machine images (e.g., Amazon Machine Images, VirtualBox images, Docker containers) for multiple platforms from a single configuration.

Installation​

To use Packer, you need to install it on your system. Installation methods vary depending on your operating system. Refer to the official Packer documentation for installation instructions.

Packer Concepts​

Builders​

Builders are responsible for creating machine images. Packer supports a variety of builders for different platforms, including AWS, Azure, VirtualBox, and more.

  • Create a machine image with a builder:
    packer build template.json

Templates​

Packer configuration files, called templates, define what builders to use and how to create machine images.

  • Create a basic Packer template:

    {
      "builders": [
        {
          "type": "builder_name",
          "...": "..."
        }
      ]
    }

  • Use variables and provisioners in templates for more advanced image creation.

Variables​

Variables in Packer templates allow you to parameterize your configuration.

  • Declare and use variables in a template:

    {
      "variables": {
        "variable_name": "default_value"
      },
      "builders": [
        {
          "type": "builder_name",
          "variable_name": "{{user `variable_name`}}"
        }
      ]
    }

  • Define variable values at runtime using -var command-line flags.

Provisioners​

Provisioners in Packer templates enable you to install and configure software on the machine image.

  • Use built-in provisioners like Shell, Ansible, or Chef to customize the image.

Post-Processors​

Post-processors allow you to transform the created machine image after the build process.

  • Examples include compressing images, copying them to a different location, or pushing them to a cloud provider.

Packer Command-Line​

  • Validate a Packer template:

    packer validate template.json

  • Build a machine image using a Packer template:

    packer build template.json

  • Inspect a machine image without building it:

    packer inspect template.json

  • Create a custom variable file and pass it during the build process:

    packer build -var-file=my-vars.json template.json

Conclusion​

This cheat sheet covers some common Packer commands and concepts. Packer simplifies the process of creating machine images for different platforms; refer to the official Packer documentation for more in-depth information and advanced usage.