atmos-packer

Atmos Packer Orchestration

Atmos wraps the Packer CLI to provide stack-aware orchestration of machine image builds. Instead of manually managing variable files, template paths, and environment configuration for each Packer component, Atmos resolves the full configuration from stack manifests and handles all of these concerns automatically.

How Atmos Orchestrates Packer

When you run any atmos packer command, Atmos performs the following sequence:

1. Resolves stack configuration -- Reads and deep-merges all stack manifests to produce the fully resolved configuration for the target component in the target stack.
2. Generates variable file -- Writes a variable file containing all vars defined for the component in the stack, making them available to the Packer template.
3. Auto-provisions source (if configured) -- If the component has a source field and the target directory does not exist, Atmos downloads the component via JIT vendoring before proceeding.
4. Resolves template path -- Determines the Packer template to use from the --template flag, settings.packer.template in the stack manifest, or defaults to . (all *.pkr.hcl files).
5. Sets environment variables -- Applies any env values defined in the stack configuration.
6. Executes the requested command -- Runs packer init, build, validate, inspect, etc. with the generated variable file and any additional flags.

This means a single command like atmos packer build ubuntu-base -s ue2-dev replaces what would normally require manually writing variable files, configuring paths, and running packer directly.

Stack Configuration

Packer components are configured under the components.packer section of stack manifests:

components:
  packer:
    ubuntu-base:
      metadata:
        type: real
        component: ubuntu-base

      settings: {}

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

      env:
        PACKER_LOG: "1"