<h1 align="center">/headless</h1>
<p align="center">
<a href="https://agentskills.io"
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alt="Agent Skills"
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<a href="https://x.com/kunchenguid"
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</p>
<h3 align="center">What if a new machine set itself up while you watched?</h3>
A Mac mini in a closet, a Linux box under the desk, a Windows PC nobody sits
at. Making one run unattended means a dozen settings at the console - never
sleep, sign in by itself after a restart, SSH keys only - and then, usually,
handing your agent the admin password so it can do the rest.
**headless** is an [Agent Skill](https://agentskills.io) that takes a machine
from "an admin account with a password and remote login on" to a configured
headless machine over SSH, one step at a time: it never sleeps, signs itself
in after a restart, takes SSH keys only, and optionally joins Tailscale. The
admin password stays in your secret store; the agent only ever names the
entry.
- **The password never reaches the agent** - it stays in Automic Vault,
1Password, Bitwarden, any command, or, as a last resort, a private env file.
The scripts read it and pipe it on; it never lands on a command line or in a
log.
- **Mac, Linux and Windows** - Apple silicon Macs with
[Determinate Nix](https://determinate.systems) and
[nix-darwin](https://github.com/nix-darwin/nix-darwin); NixOS with this
repository's NixOS module, any other distribution replaced with NixOS by
[nixos-anywhere](https://github.com/nix-community/nixos-anywhere) if you
choose, or Debian, Ubuntu and Fedora kept with a distro-neutral script;
Windows 11 and Windows Server 2025 with a rerunnable PowerShell script over
OpenSSH.
- **Every step reruns safely** - each step says what it does, runs, and shows
its result; the last step reads every setting back, restarts the machine
and checks it comes back.
- **Proven end to end** - each platform's whole journey runs on a
GitHub-hosted runner over SSH to itself, and the logs are checked for the
password.
## Quick Start
```sh
# install (global recommended)
$ npx skills add kunchenguid/headless -g
# in your agent
/headless set up my Mac mini at 192.168.1.20 as a headless machine
```
## What it needs
- **Your computer:** macOS or Linux with bash, ssh and tar (and Nix, only to
install NixOS on a Linux machine).
- **The machine:** an Apple silicon Mac on a current macOS, an x86_64 or
aarch64 Linux machine with systemd, or a Windows 11 or Windows Server 2025
PC - with an admin account that has a password, and remote login on.
- **A secret store** for that password. Tailscale is optional.
## How It Works
For a Mac the skill walks you through seven steps:
```
admin account + password + Remote Login on
โ
โผ
โโโโโโโโโโโโโโโโโโโโโโ
โ admin access โ you, once, at the Mac
โโโโโโโโโโโฌโโโโโโโโโโโ
โผ
โโโโโโโโโโโโโโโโโโโโโโ
โ save the password โ you, once, in your secret store
โโโโโโโโโโโฌโโโโโโโโโโโ
โผ
โโโโโโโโโโโโโโโโโโโโโโ
โ config folder โ on your computer, from this repository's default config
โโโโโโโโโโโฌโโโโโโโโโโโ
โผ
โโโโโโโโโโโโโโโโโโโโโโ
โ first SSH sign-in โ host key pinned ยท your key added
โโโโโโโโโโโฌโโโโโโโโโโโ
โผ
โโโโโโโโโโโโโโโโโโโโโโ
โ admin session โ Determinate Nix ยท FileVault off ยท automatic sign-in
โโโโโโโโโโโฌโโโโโโโโโโโ
โผ
โโโโโโโโโโโโโโโโโโโโโโ
โ apply โ the config ยท Tailscale if you want it
โโโโโโโโโโโฌโโโโโโโโโโโ
โผ
โโโโโโโโโโโโโโโโโโโโโโ
โ verify + restart โ every setting read back ยท the Mac comes back
โโโโโโโโโโโฌโโโโโโโโโโโ
โผ
headless Mac
```
A Linux machine takes the same path, without the admin session: after the
first sign-in, a machine on NixOS is applied as it is; on another
distribution you choose between installing NixOS (the whole disk is erased)
and keeping it with the script.
A Windows PC starts with a few lines you paste in an administrator
PowerShell to turn OpenSSH Server on (and, on a home or office network
Windows calls Public, to mark it Private so SSH gets through the firewall).
After the first sign-in, applying the config sets key-only SSH, automatic
sign-in (the password kept as an LSA secret), the extras and Tailscale.
## Usage
| Invoke | Example |
| ------ | ------- |
| Slash | `/headless set up my Mac mini at 192.168.1.20 as a headless machine` |
| Natural language | "update my headless Linux server and check it comes back after a restart" |
The agent should auto-invoke when asked to set up, configure, update or check
a machine you reach only over SSH.
## Package layout
```
skills/headless/
SKILL.md # the agent contract: the rules and every step
references/ # mac.md ยท linux.md ยท windows.md ยท secrets.md ยท tailscale.md
scripts/ # mac/ ยท linux/ ยท windows/: connect, apply, verify, restart, tailscale
assets/ # darwin/ ยท nixos/ ยท windows/: the default configs the skill copies
modules/
darwin/headless.nix # the nix-darwin module, darwinModules.headless
nixos/headless.nix # the NixOS module, nixosModules.headless
flake.nix # the modules, templates.darwin (default) and templates.nixos
tests/ # the secret helper's test and the Mac, Linux and Windows journeys CI runs
```
Ships as an [`npx skills`](https://github.com/vercel-labs/skills) package.
The repository is also a Nix flake, and the modules are the layers the skill
applies. Use them from your own flake:
```nix
inputs.headless.url = "github:kunchenguid/headless";
# in your darwinSystem modules:
headless.darwinModules.headless
{ headless = { user = "admin"; sshKeys = [ "ssh-ed25519 ..." ]; }; }
```
`nixosModules.headless` is used the same way in a `nixosSystem`. The options
are listed in `skills/headless/references/mac.md` and
`skills/headless/references/linux.md`.
`nix flake init -t github:kunchenguid/headless#nixos` (or `#darwin`) gives the
starting config the skill copies, the NixOS one with a disko disk layout for
new installs.
## Development
```sh
# edit the skill
$EDITOR skills/headless/SKILL.md
# smoke-test discovery locally
npx skills add ./ -l
# install from this checkout
npx skills add ./ -g -y
# checks
nix flake check # modules and default configs build (this system's)
tests/secret-run.test.sh # the password is piped, never printed
shellcheck -x tests/*.sh skills/headless/scripts/*.sh skills/headless/scripts/*/*.sh skills/headless/scripts/*/remote/*.sh
```
The `mac` workflow runs the whole journey on a GitHub-hosted Mac, over SSH
to itself. The `linux` workflow runs the distro-neutral script on a
GitHub-hosted Ubuntu runner over SSH to itself, and installs NixOS with
nixos-anywhere on an x86_64 Ubuntu virtual machine there, then applies,
restarts and verifies it. The `windows` workflow checks every PowerShell
file parses, then runs the Windows journey on a GitHub-hosted Windows Server
runner over SSH to itself, from Ubuntu under WSL. Each checks its log never
holds the password.
Pull requests to `main` are raised through
[no-mistakes](https://github.com/kunchenguid/no-mistakes): the
`PR must be raised via no-mistakes` check stays red on a pull request opened
by hand until its branch is pushed through the gate (`git push no-mistakes`),
which writes a pipeline attestation into the pull request's description.
