# Using Packer

Atmos natively supports opinionated workflows for [HashiCorp Packer](https://www.packer.io/). 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](/cli/commands/packer/usage) 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:

```yaml
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:**
  ```yaml
  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](/stacks/components#metadata-attributes) for details.

  **Example:**
  ```yaml
  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:**
  ```yaml
  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:

```shell
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:

```shell
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:

```shell
atmos packer validate ubuntu-base -s ue2-dev
```

## Example: Inspect a Packer Template

To inspect a Packer template and see its configuration:

```shell
atmos packer inspect ubuntu-base -s ue2-dev
```