added readme and updated auto-install.sh script to dynamically derive hostnames from flake

README.md

@@ -0,0 +1,102 @@
+# 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
+  ```
+

installer.nix

@@ -12,7 +12,7 @@
   services.openssh.settings.PermitRootLogin = "yes";
 
   environment.systemPackages = with pkgs; [
-    git curl parted e2fsprogs btrfs-progs util-linux
+    git curl jq parted e2fsprogs btrfs-progs util-linux
   ];
 
 #  environment.etc."flake-url".text = "git+https://gitea.lan.ddnsgeek.com/beatzaplenty/nixos.git?ref=main#nixos";   
@@ -38,8 +38,18 @@ environment.etc."git-credentials".text =
 
 export FLAKE_BASE_URL="git+https://gitea.lan.ddnsgeek.com/beatzaplenty/nixos.git"
 
-# Menu options
+echo "Fetching available NixOS hosts from flake..."
-options=("nixos" "docker" "server" "nix-cache" "nix-minimal")
+mapfile -t options < <(
+  nix eval --json --no-use-registries --no-accept-flake-config \
+    "''${FLAKE_BASE_URL}#nixosConfigurations" \
+    --apply builtins.attrNames \
+  | jq -r '.[]'
+)
+
+if [[ ''${#options[@]} -eq 0 ]]; then
+  echo "ERROR: No NixOS hosts found in ''${FLAKE_BASE_URL}#nixosConfigurations" >&2
+  exit 1
+fi
 
 echo "Choose the flake profile to install:"
 select choice in "''${options[@]}"; do

result

@@ -0,0 +1 @@
+/nix/store/qrx1ipw9azj3as3y93l9g5sjxpk20jaz-nixos-minimal-25.05.20250112.2f9e2f8-x86_64-linux.iso