Packer — Automated Machine Image Building for Any Platform

What it is

Packer is HashiCorp's open-source tool for creating identical machine images across multiple platforms from a single source configuration. It supports Amazon AMIs, Docker images, Google Compute Engine images, VMware templates, and many more builders through a plugin system.

Infrastructure engineers, DevOps teams, and platform teams use Packer to enforce consistency between development, staging, and production environments. By baking all dependencies into a machine image, you eliminate configuration drift that occurs when provisioning servers at boot time.

How it saves time or tokens

Without Packer, teams either provision servers at boot time (slow, error-prone) or manually create and snapshot images (inconsistent, undocumented). Packer automates the entire process: launch a temporary instance, run provisioners (shell scripts, Ansible, Chef), capture the image, and destroy the instance. The result is a versioned, reproducible artifact.

A single packer build command replaces a multi-step manual process that typically takes 30-60 minutes of an engineer's time per image variant.

How to use

1. Install Packer:

brew install packer

1. Write an HCL template and build:

packer init aws.pkr.hcl
packer validate aws.pkr.hcl
packer build aws.pkr.hcl

1. The output is a machine image ID (AMI, Docker tag, etc.) ready for deployment.

Example

A Packer HCL template for building an AWS AMI:

packer {
  required_plugins {
    amazon = {
      source  = "github.com/hashicorp/amazon"
      version = "~> 1.3"
    }
  }
}

source "amazon-ebs" "ubuntu" {
  ami_name      = "my-app-{{timestamp}}"
  instance_type = "t3.micro"
  region        = "us-east-1"
  source_ami    = "ami-0c7217cdde317cfec"
  ssh_username  = "ubuntu"
}

build {
  sources = ["source.amazon-ebs.ubuntu"]
  provisioner "shell" {
    inline = [
      "sudo apt-get update -y",
      "sudo apt-get install -y nginx"
    ]
  }
}

This template launches a t3.micro instance, installs nginx, and captures the result as a timestamped AMI.

Related on TokRepo

• DevOps Tools -- Infrastructure automation tools for building and deploying
• Automation Tools -- CI/CD pipelines and build automation workflows

Common pitfalls

• Forgetting packer init before the first build. Packer 1.7+ requires explicit plugin installation via init, and builds fail without it.
• Not cleaning up old AMIs. Each build creates a new image; set up a lifecycle policy or script to deregister images older than N days.
• Provisioner ordering matters. Shell provisioners run sequentially; if an early step fails, subsequent steps may succeed silently with a broken base. Use set -e in shell scripts.