Hashicorp Packer

Packer is an open source tool for creating identical machine images for multiple platforms from a single source configuration. Packer is lightweight, runs on every major operating system, and is highly performant, creating machine images for multiple platforms in parallel. Packer does not replace configuration management like Chef, Puppet or Ansible. In fact, when building images, Packer is able to use tools like Chef, Puppet or Ansible to install software onto the image.

A machine image is a single static unit that contains a pre-configured operating system and installed software which is used to quickly create new running machines. Machine image formats change for each platform.

jamlab-packer: Packer configurations for building homelab images. This repository contains my configurations for images.

Usageඞ

With the Proxmox Builder (ISO) it is possible to use a remote or local ISO file to create and configure a VM which can be converted into a template that can be used for super fast provisioning of VMs.

Commandsඞ

Install dependencies and modules:

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packer init -upgrade .

After configuring everything, building images is as easy as running a single command. PACKER_LOG=1 is used to print detailed messages while building for easier debugging:

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PACKER_LOG=1 packer build debian11.pkr.hcl

With log output to a file:

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PACKER_LOG_PATH="packerlog.txt" PACKER_LOG=1 packer build debian11.pkr.hcl

Where debian11.pkr.hcl is the configuration file that defines how to build the image.

Variablesඞ

Defining variables in HCL:

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variable "iso_checksum" {
  type    = string
  default = "e307d0e583b4a8f7e5b436f8413d4707dd4242b70aea61eb08591dc0378522f3"
}

Defined variables can be used like so:

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iso_checksum = var.iso_checksum

Or also substituted into other strings:

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iso_full_url = "https://${var.iso_url}${var.iso_checksum}"

Preseedඞ

Preseeding provides a way to answer questions asked during the installation process without having to manually enter the answers while the installation is running. Read more about this method in the preseed documentation.

With preseed I configure the bare minimum for the installation to work before the cloud-init takes over.

Cloud-initඞ

Cloud-init is used for initial machine configuration like creating users, installing packages, custom scripts or preseeding authorized_keys file for SSH authentication. Read more about this in cloud-init documentation.

With cloud-init I reset the root password to something randomized, install necessary packages for Ansible to take over the configuration and initialize the script that checks if Ansible management is bootstrapped.