🍞 What Even Is Packer?

Packer is a tool that lets you create pre-configured machine images for multiple platforms from a single source template.

Think of it like baking a cake (machine image) using a recipe (template), and then freezing it so you can instantly microwave it later (deploy that sucker in seconds).

Instead of spinning up a fresh VM every time and manually installing stuff like a caveman, you use Packer to automate the whole thing.

🧙‍♂️ A Brief History of Packer

Back in the foggy year of 2013, a magical DevOps wizard named Mitchell Hashimoto created Packer.

Why? Because back then, building VM images was the Wild West:

• People were SSHing into machines and manually setting them up 😱
• Nothing was repeatable
• Every environment had “its own special snowflake” config
• CI/CD pipelines wept bitter tears

So Mitchell said, “Let there be images!” And Packer was born.

Since then, it’s become the go-to tool for building immutable infrastructure.

🎮 Packer: How It Works

At its core, Packer uses a template file (nowadays written in HashiCorp Configuration Language, aka HCL) that describes:

• 🔨 Builders – What platform are you building for? AWS, Azure, Docker, VMware, etc.
• 🧙‍♀️ Provisioners – How do you configure it? Shell, Ansible, etc.
• 📦 Post-processors – What to do afterward? Compress it, upload it, show it off on Instagram?

Let’s look at a simple example…

🧰 Packer Example: AWS AMI with Nginx

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# nginx-ami.pkr.hcl

source "amazon-ebs" "nginx" {
  ami_name      = "nginx-ami-{{timestamp}}"
  instance_type = "t2.micro"
  region        = "us-east-1"
  source_ami    = "ami-0c55b159cbfafe1f0" # Ubuntu 20.04 in us-east-1
  ssh_username  = "ubuntu"
}

build {
  sources = ["source.amazon-ebs.nginx"]

  provisioner "shell" {
    inline = [
      "sudo apt-get update",
      "sudo apt-get install -y nginx",
      "sudo systemctl enable nginx"
    ]
  }
}

To build it:

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packer init .
packer fmt .
packer validate nginx-ami.pkr.hcl
packer build nginx-ami.pkr.hcl

Boom. 🎉 Now you’ve got an AMI with Nginx already baked in, ready to roll on AWS. No more configuring on the fly like some kind of IT goblin.

🧱 Use Cases for Packer

• 🔄 CI/CD Pipelines – Build an image with app + dependencies, then deploy it anywhere.
• ☁️ Cloud Deployments – Create AWS AMIs, Azure images, or GCP disks.
• 🖥️ Local Testing – Create VirtualBox/Vagrant images for dev environments.
• 🐳 Docker – Yep, Packer can even build Docker images!

🧑‍🍳 The DevOps Kitchen Analogy

🚫 What Packer Is NOT

• It’s not a configuration management tool (like Ansible or Chef)
• It’s not a cloud deployer (like Terraform — though they’re BFFs)
• It won’t clean your kitchen (but it will clean up your infrastructure)

🧞 Tips & Tricks

• Use packer fmt to format your template like a civilized human
• Use packer validate to catch errors before you waste 10 minutes of your life
• Name your AMIs/images with timestamps or version tags to stay sane
• Commit your Packer templates — they’re code!

💥 Final Thoughts: Pack It Up, Pack It In

Packer is one of those tools that feels like magic once you start using it. You go from “Wait, I have to install Nginx again?” to “Oh yeah, my CI pipeline bakes fresh images with that already included.”

It’s fast, it’s scriptable, and it’s totally open source.

Plus, once you’ve baked your golden images, you can deploy them confidently — no surprises, no config drift, no Todd breaking production again.

🔑 Key Ideas