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Using Packer

Atmos natively supports opinionated workflows for HashiCorp Packer. Packer automates the creation of machine images for multiple platforms, enabling you to build immutable infrastructure with consistent, versioned images.

For a complete list of supported commands, please see the Atmos packer documentation.

Why Use Packer with Atmos?​

Packer components in Atmos allow you to:

  • Build immutable infrastructure — Create golden AMIs and machine images that are versioned and reproducible
  • Patch images for security and compliance — Apply security patches and compliance requirements consistently across your image library
  • Manage images like any other component — Use the same inheritance, imports, and configuration patterns you use for Terraform

Stack Configuration​

The schema for configuring Packer components in Atmos stacks:

components:
  packer:
    # the slug of the component
    ubuntu-base:

      # configuration specific to atmos
      metadata:
        type: real
        component: ubuntu-base

      # Settings for integrations
      settings: {}

      # Variables passed to Packer
      vars:
        ami_name: "ubuntu-base"
        instance_type: "t3.medium"
        source_ami_filter_name: "ubuntu/images/hvm-ssd/ubuntu-jammy-22.04-amd64-server-*"

      # Environment variables
      env:
        PACKER_LOG: "1"

Attributes​

vars (optional)

Variables passed to Packer. These are deep-merged and made available to your Packer templates.

Example:

vars:
  ami_name: "ubuntu-base"
  instance_type: "t3.medium"
  region: "us-east-1"
metadata (optional)

The metadata section extends functionality of the component. See Common Component Attributes for details.

Example:

metadata:
  type: real
  component: ubuntu-base
  inherits:
    - base-image-defaults
settings (optional)

Free-form map for integration configuration.

env (optional)

Environment variables to set when running Packer commands.

Example:

env:
  PACKER_LOG: "1"
  AWS_PROFILE: "production"

Example: Build a Packer Component​

To build a Packer component using the atmos CLI, run the following commands:

atmos packer init ubuntu-base --stack=ue2-dev
atmos packer build ubuntu-base --stack=ue2-dev

where:

  • ubuntu-base is the Packer component to build (from the components/packer folder)
  • --stack=ue2-dev is the stack context for the build

Short versions of the command-line arguments can be used:

atmos packer init ubuntu-base -s ue2-dev
atmos packer build ubuntu-base -s ue2-dev

Example: Validate a Packer Template​

To validate a Packer template before building:

atmos packer validate ubuntu-base -s ue2-dev

Example: Inspect a Packer Template​

To inspect a Packer template and see its configuration:

atmos packer inspect ubuntu-base -s ue2-dev