Sovran_SystemsOS/docs/remote-deploy-headscale.md

Remote Deployment via Headscale (Self-Hosted Tailscale)

This guide covers the Sovran Systems remote deployment system built on Headscale — a self-hosted, open-source implementation of the Tailscale coordination server. Freshly booted ISOs automatically join a private WireGuard mesh VPN without any per-machine key pre-generation.

---

Architecture Overview

┌─────────────────────────────────────────────────────────┐
│                        Internet                          │
└────────────┬─────────────────────┬──────────────────────┘
             │                     │
             ▼                     ▼
┌────────────────────┐   ┌─────────────────────────────────┐
│   Admin Workstation │   │         Sovran VPS              │
│                    │   │  ┌─────────────────────────────┐ │
│  tailscale up      │   │  │  Headscale (port 8080)      │ │
│  --login-server    │◄──┼─►│  Coordination server        │ │
│  hs.example.com   │   │  ├─────────────────────────────┤ │
│                    │   │  │  Provisioning API (9090)    │ │
└────────────────────┘   │  │  POST /register             │ │
                         │  │  GET  /machines             │ │
                         │  │  GET  /health               │ │
                         │  ├─────────────────────────────┤ │
                         │  │  Caddy (80/443)             │ │
                         │  │  hs.example.com → :8080     │ │
                         │  │  prov.example.com → :9090   │ │
                         │  └─────────────────────────────┘ │
                         └─────────────────────────────────┘
                                        ▲
                                        │  WireGuard mesh (Tailnet)
                                        ▼
                         ┌─────────────────────────────────┐
                         │     Deploy Target Machine       │
                         │                                 │
                         │  Boot live ISO →               │
                         │  sovran-auto-provision →       │
                         │  POST /register →              │
                         │  tailscale up --authkey=...    │
                         └─────────────────────────────────┘

Components:

• sovran-provisioner.nix — NixOS module deployed on a separate VPS; runs Headscale + provisioning API + Caddy.
• Live ISO (iso/common.nix) — Auto-registers with the provisioning server and joins the Tailnet on boot.
• remote-deploy.nix — Post-install NixOS module that uses Tailscale/Headscale for ongoing access.

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Part 1: VPS Setup — Deploy sovran-provisioner.nix

Prerequisites

• A NixOS VPS (any provider) with a public IP
• Two DNS A records pointing to your VPS:
  • hs.yourdomain.com → VPS IP (Headscale coordination server)
  • prov.yourdomain.com → VPS IP (Provisioning API)
• Ports 80, 443 (TCP) and 3478 (UDP, STUN/DERP) open in your VPS firewall

DNS Records

Type	Name	Value
A	hs.yourdomain.com	<VPS IP>
A	prov.yourdomain.com	<VPS IP>

NixOS Configuration

Add the following to your VPS's /etc/nixos/configuration.nix:

{ config, lib, pkgs, ... }:

{
  imports = [
    ./hardware-configuration.nix
    /path/to/sovran-provisioner.nix   # or fetch from the repo
  ];

  sovranProvisioner = {
    enable = true;
    domain        = "prov.yourdomain.com";
    headscaleDomain = "hs.yourdomain.com";

    # Optional: customise defaults
    headscaleUser = "sovran-deploy";   # namespace for deploy machines
    adminUser     = "admin";           # namespace for your workstation
    keyExpiry     = "1h";              # pre-auth keys expire after 1 hour
    rateLimitMax  = 10;                # max registrations per window
    rateLimitWindow = 60;              # window in seconds
  };

  # Required for Caddy ACME (Let's Encrypt)
  networking.hostName = "sovran-vps";
  system.stateVersion = "24.11";
}

Deploy

nixos-rebuild switch

Caddy will automatically obtain TLS certificates via Let's Encrypt.

Retrieve the Enrollment Token

cat /var/lib/sovran-provisioner/enroll-token

Keep this token secret — it is used to authenticate ISO registrations. The token is auto-generated on first boot and stored at this path. You never need to set it manually. Just cat it from the VPS and copy it to iso/secrets/enroll-token before building the ISO.

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Part 2: Admin Workstation Setup

Join your Tailnet as an admin so you can reach deployed machines:

Install Tailscale

Follow the Tailscale installation guide for your OS, or on NixOS:

services.tailscale.enable = true;

Join the Tailnet

sudo tailscale up --login-server https://hs.yourdomain.com

Tailscale prints a URL. Open it and copy the node key (starts with mkey:).

Approve the Node in Headscale

On the VPS:

headscale nodes register --user admin --key mkey:xxxxxxxxxxxxxxxx

Your workstation is now on the Tailnet. You can list nodes:

headscale nodes list

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Part 3: Building the Deploy ISO

Add Secrets (gitignored)

The secrets directory iso/secrets/ is gitignored. Populate it before building:

# Copy the enrollment token from the VPS
ssh root@<VPS> cat /var/lib/sovran-provisioner/enroll-token > iso/secrets/enroll-token

# Set the provisioner URL
echo "https://prov.yourdomain.com" > iso/secrets/provisioner-url

These files are baked into the ISO at build time. If the files are absent the ISO still builds — the auto-provision service exits cleanly with "No enroll token found, skipping auto-provision", leaving DIY users unaffected.

Build the ISO

nix build .#nixosConfigurations.sovran_systemsos-iso.config.system.build.isoImage

The resulting ISO is in ./result/iso/.

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Part 4: Deployment Workflow

Step-by-Step

1. Hand the ISO to the remote person — they burn it to a USB drive and boot.

2. ISO boots and auto-registers — sovran-auto-provision.service runs automatically:

   • Reads enroll-token and provisioner-url from /etc/sovran/
   • POST https://prov.yourdomain.com/register with hostname + MAC
   • Receives a Headscale pre-auth key
   • Runs tailscale up --login-server=... --authkey=...
   • The machine appears in headscale nodes list within ~30 seconds

3. Approve the node (if not using auto-approve) — on the VPS:

   headscale nodes list
   # Note the node key for the new machine
   

4. SSH from your workstation — once the machine is on the Tailnet:

   # Get the machine's Tailscale IP
   headscale nodes list | grep sovran-deploy-
   
   # SSH in
   ssh root@100.64.x.x    # password: sovran-remote (live ISO default)
   

5. Run the headless installer:

   The --deploy-key is your SSH public key that gets injected into root's authorized_keys on the deployed machine. This grants full root access for initial setup. Generate it once on your workstation if you haven't already:

   ssh-keygen -t ed25519 -f ~/.ssh/sovran-deploy -C "sovran-deploy"
   

   After deployment is complete and you disable deploy mode, this key is removed.

   sudo sovran-install-headless.sh \
     --disk /dev/sda \
     --role server \
     --deploy-key "$(cat ~/.ssh/sovran-deploy.pub)" \
     --headscale-server "https://hs.yourdomain.com" \
     --headscale-key "$(headscale preauthkeys create --user sovran-deploy --expiration 2h --output json | jq -r '.key')"
   

6. Machine reboots into Sovran_SystemsOS — deploy-tailscale-connect.service runs:

   • Reads /var/lib/secrets/headscale-authkey
   • Joins the Tailnet with a deterministic hostname (sovran-<hostname>)

7. Post-install SSH and RDP:

   # SSH over Tailnet
   ssh root@<tailscale-ip>
   
   # RDP over Tailnet (desktop role) — Sovran_SystemsOS uses GNOME Remote Desktop (native Wayland RDP)
   # Retrieve the auto-generated RDP password:
   ssh root@<tailscale-ip> cat /var/lib/gnome-remote-desktop/rdp-password
   # Then connect with any RDP client (Remmina, GNOME Connections, Microsoft Remote Desktop):
   #   Host: <tailscale-ip>:3389   User: sovran   Password: <from above>
   

8. Disable deploy mode — edit /etc/nixos/custom.nix on the target, set enable = false, then:

   sudo nixos-rebuild switch
   

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Part 5: Post-Install Access

SSH

# Over Tailnet
ssh root@100.64.x.x

RDP (desktop/server roles)

Sovran_SystemsOS uses GNOME Remote Desktop (native Wayland RDP — not xfreerdp). The RDP service auto-generates credentials on first boot.

Username: sovran Password: auto-generated — retrieve it via SSH:

ssh root@<tailscale-ip> cat /var/lib/gnome-remote-desktop/rdp-password

Connect using any RDP client (Remmina, GNOME Connections, Microsoft Remote Desktop) to <tailscale-ip>:3389.

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Security Model

Concern	Mitigation
Enrollment token theft	Token only triggers key generation; it does not grant access to the machine itself
Rogue device joins Tailnet	Visible in headscale nodes list; removable instantly with headscale nodes delete
Pre-auth key reuse	Keys are ephemeral and expire in 1 hour (configurable via keyExpiry)
Rate limiting	Provisioning API limits to 10 registrations/minute by default (configurable)
SSH access	Requires ed25519 key injected at install time; password authentication disabled
Credential storage	Auth key written to /var/lib/secrets/headscale-authkey (mode 600) on the installed OS

Token Rotation

To rotate the enrollment token:

1. On the VPS:

   openssl rand -hex 32 > /var/lib/sovran-provisioner/enroll-token
   chmod 600 /var/lib/sovran-provisioner/enroll-token
   

2. Update iso/secrets/enroll-token and rebuild the ISO.

Old ISOs with the previous token will fail to register (receive 401).

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Monitoring

List Active Tailnet Nodes

# On the VPS
headscale nodes list

List Registered Machines (Provisioning API)

curl -s -H "Authorization: Bearer $(cat /var/lib/sovran-provisioner/enroll-token)" \
  https://prov.yourdomain.com/machines | jq .

Health Check

curl https://prov.yourdomain.com/health
# {"status": "ok"}

Provisioner Logs

journalctl -u sovran-provisioner -f

Headscale Logs

journalctl -u headscale -f

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Cleanup

Remove a Machine from the Tailnet

headscale nodes list
headscale nodes delete --identifier <id>

Disable Deploy Mode on an Installed Machine

Edit /etc/nixos/custom.nix:

sovran_systemsOS.deploy.enable = false;

Then rebuild:

nixos-rebuild switch

This stops the Tailscale connect service.

Revoke All Active Pre-Auth Keys

headscale preauthkeys list --user sovran-deploy
headscale preauthkeys expire --user sovran-deploy --key <key>

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Reference

Component	Port	Protocol	Description
Caddy	80	TCP	HTTP → HTTPS redirect
Caddy	443	TCP	HTTPS (Let's Encrypt)
Headscale	8080	TCP	Coordination server (proxied by Caddy)
Provisioner	9090	TCP	Registration API (proxied by Caddy)
DERP/STUN	3478	UDP	WireGuard relay fallback
Tailscale	N/A	WireGuard	Mesh VPN between nodes