Book Image

HashiCorp Packer in Production

By : John Boero
Book Image

HashiCorp Packer in Production

By: John Boero

Overview of this book

Creating machine images can be time-consuming and error-prone when done manually. HashiCorp Packer enables you to automate this process by defining the configuration in a simple, declarative syntax. This configuration is then used to create machine images for multiple environments and cloud providers. The book begins by showing you how to create your first manifest while helping you understand the available components. You’ll then configure the most common built-in builder options for Packer and use runtime provisioners to reconfigure a source image for desired tasks. You’ll also learn how to control logging for troubleshooting errors in complex builds and explore monitoring options for multiple logs at once. As you advance, you’ll build on your initial manifest for a local application that’ll easily migrate to another builder or cloud. The chapters also help you get to grips with basic container image options in different formats while scaling large builds in production. Finally, you’ll develop a life cycle and retention policy for images, automate packer builds, and protect your production environment from nefarious plugins. By the end of this book, you’ll be equipped to smoothen collaboration and reduce the risk of errors by creating machine images consistently and automatically based on your defined configuration.
Table of Contents (18 chapters)
1
Part 1: Packer’s Beginnings
7
Part 2: Managing Large Environments
11
Part 3: Advanced Customized Packer

Simplifying your template with variables

Variables can be declared in HCL2 in a very similar way to how Terraform declares variables: create a variable block, give it a name, give it a description and type (optional), and specify an optional default value. Here, we will create a variable called iso that defaults to a download URL. This may be referenced in the code directly as var.iso or it can be used with standard shell interpolation in strings, as in ${var.creds.user}, which helps with templating:

variable "iso" {
  description = "The path to your ISO."
  type = string
  default = "https://fqdn/media/base.iso"
}

Local variables differ from normal variables in that they can’t be assigned as parameters. Locals offer a simple way to declare reusable values in your code without allowing the runner to specify them as parameters. You can think of variables as public parameters and locals as private variables, which...