# Nix Auto Installer

This repository builds a custom NixOS installer ISO that can install one of the
hosts exposed by a separate NixOS flake.

The ISO is intentionally opinionated for a local environment. When the `nixos`
user logs in, it runs `/etc/auto-install.sh`, asks which flake host to install,
partitions `/dev/sda`, installs NixOS, and reboots.

## Repository Layout

- `flake.nix` defines the build output. The default package is an
  `install-iso` image produced with `nixos-generators`.
- `installer.nix` defines the installer ISO configuration, including SSH,
  Git credentials, users, and the generated auto-install script.

## Requirements

- A machine with Nix installed and flakes enabled.
- Network access to the configured NixOS flake repository.
- A target machine or VM where `/dev/sda` is the disk you want to erase.

## Build The ISO

From the repository root:

```sh
nix build
```

The generated ISO will be available through the `result` symlink.

## Use The Installer

1. Boot the generated ISO on the target machine.
2. Log in as the `nixos` user, or connect over SSH if networking is available.
3. The login shell runs `/etc/auto-install.sh`.
4. Choose one of the hosts returned by:

   ```sh
   nix eval --json --no-use-registries --no-accept-flake-config \
     "git+https://gitea.lan.ddnsgeek.com/beatzaplenty/nixos.git#nixosConfigurations" \
     --apply builtins.attrNames
   ```

5. Confirm the install when prompted.

## What The Installer Does

The generated `/etc/auto-install.sh` script:

1. Reads available host names from the configured flake.
2. Prompts for the host profile to install.
3. Asks for confirmation.
4. Repartitions `/dev/sda` with an MBR layout:
   - `/dev/sda1`: ext4 root filesystem labeled `nixos`
   - `/dev/sda2`: swap partition labeled `swap`
5. Mounts the new root filesystem at `/mnt`.
6. Runs `nixos-install --flake`.
7. Reboots the machine.

## Configuration Notes

The installer currently assumes:

- The flake to install is
  `git+https://gitea.lan.ddnsgeek.com/beatzaplenty/nixos.git`.
- Install targets are exposed under `#nixosConfigurations`.
- The install disk is always `/dev/sda`.
- The timezone is `Australia/Brisbane`.
- SSH is enabled and root login is permitted.
- The generated ISO has both `root` and `nixos` users configured with hashed
  passwords.

Change these values in `installer.nix` before building if your environment
differs.

## Safety Warnings

This installer is destructive. Once confirmed, it repartitions `/dev/sda`
without another prompt. Make sure the target disk name is correct before using
the ISO on real hardware.

`installer.nix` currently contains embedded Git credentials, password hashes,
and an SSH public key. Treat this repository and any generated ISO as sensitive.
Prefer moving credentials to a safer delivery mechanism before sharing the repo
or ISO.

## Troubleshooting

- If no host choices appear, confirm the target machine has network access and
  can reach the configured flake URL.
- If installation fails while fetching the flake, verify the embedded Git
  credentials are valid.
- If the wrong disk is being partitioned, stop immediately and update the disk
  paths in `installer.nix`.
- If the login shell does not start the installer, run it manually:

  ```sh
  sudo /etc/auto-install.sh
  ```