https://github.com/mhutter/hcloud-packer-coreos

CoreOS Packer template for Hetzner Cloud
https://github.com/mhutter/hcloud-packer-coreos

Last synced: 25 days ago
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CoreOS Packer template for Hetzner Cloud

• Host: GitHub
• URL: https://github.com/mhutter/hcloud-packer-coreos
• Owner: mhutter
• Created: 2023-09-01T16:15:48.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2024-10-29T21:52:38.000Z (about 2 months ago)
• Last Synced: 2024-10-29T23:49:08.384Z (about 2 months ago)
• Language: HCL
• Homepage:
• Size: 48.8 KB
• Stars: 9
• Watchers: 2
• Forks: 0
• Open Issues: 3
• Metadata Files:
  • Readme: README.md

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README

        
# CoreOS Packer template for Hetzner Cloud

This template builds a fully functioning Fedora CoreOS image on [Hetzner Cloud](https://hetzner.cloud/?ref=72AtIaBWO7Uw)[^1]

[^1]: Use this link to get €20 cloud balance for free. If you spend money with Hetzner Cloud, I get €10 as kickback.

## Features

- Support for Ignition configs provided via user data

- Automatic configuration of SSH public keys for `core` user

- Hostname configuration

- Support for `Arm64 (Ampere)`

## Usage

Prerequisites:

- [Packer](https://developer.hashicorp.com/packer/downloads?product_intent=packer)

- [Butane](https://coreos.github.io/butane/getting-started/)

(If you use Nix, just run `nix develop` to get a shell with those tools available)

```sh

export HCLOUD_TOKEN='helpiamtrappedinatokengenerator'

make build

```

## How it works

Image-building itself is straight forward:

1. provision any Linux server & boot in rescue mode

1. stream the CoreOS raw disk image onto `/dev/sda`

1. write a "chainloading" Ignition config (see below)

Now, the biggest challenge is configuring CoreOS systems properly. For Hetzner-provided images, `cloud-init` takes care of those things:

- set the hostname

- configure SSH public keys for `root`

- apply configuration provided as "user data"

CoreOS however only supports Ignition (a `cloud-init` alternative developed by CoreOS), which does not yet know how to talk to the Hetzner metadata/userdata service (PRs are open since 2018 ...).

We work around this by applying a few hacks (see [`files/chain.bu`](./files/chain.bu)):

- Configure a remote Ignition config to be merged into the statically provisioned one. As the source we configure the Hetzner userdata endpoint (`http://169.254.169.254/hetzner/v1/userdata`). This allows us to just use Ignition configs as userdata.

- Write `/etc/hostname` based on data from the Hetzner metadata endpoint (`http://169.254.169.254/hetzner/v1/metadata/hostname`)

- Write a Systemd service that downloads & installs the SSH public keys as authorized keys for the preconfigured `core` user.

## Further Reading

- [Hetzner Cloud Builder for Packer](https://developer.hashicorp.com/packer/integrations/hetznercloud/hcloud)