Add NixOS server installer USB (disko LUKS + WiFi, hostname prompt)

- disko-server.nix: LUKS + ESP + ext4 root layout for disko-install
- server-install: minimal NixOS config for new servers (hostname/WiFi via --system-config)
- installer-iso: custom minimal ISO with iwlwifi; build with nix build .#installer-iso
- scripts/nixos-server-install.sh: prompt hostname/disk, run disko-install
- docs/server-installer-usb.md: build, write USB, optional live/installed WiFi
- .gitignore: nixos/installer-wifi.nix; AGENTS.md + README.md notes

Made-with: Cursor

scripts/nixos-server-install.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+# Run on a NixOS minimal live system (or installer ISO) to install NixOS with
+# disko (LUKS + root). Prompts for hostname and target disk; optionally use
+# INSTALLER_SYSTEM_CONFIG_FILE for WiFi etc.
+#
+# Usage:
+#   Export FLAKE_REF (e.g. github:User/dotfiles or path:/path/to/dotfiles/nixos).
+#   Or run from repo root and use: FLAKE_REF=path:$(pwd)/nixos
+#   sudo ./scripts/nixos-server-install.sh
+#   # or: sudo FLAKE_REF=github:User/dotfiles ./scripts/nixos-server-install.sh
+#
+# Optional: INSTALLER_SYSTEM_CONFIG_FILE=/path/to/json with full --system-config
+# (e.g. hostName + networking.wireless.networks). If unset, only hostname is passed.
+set -euo pipefail
+
+FLAKE_REF="${FLAKE_REF:-}"
+if [[ -z "$FLAKE_REF" ]]; then
+  if [[ -d "$(dirname "$0")/../nixos" ]] && [[ -f "$(dirname "$0")/../nixos/flake.nix" ]]; then
+    REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+    FLAKE_REF="path:${REPO_ROOT}/nixos"
+  else
+    echo "FLAKE_REF not set and not running from dotfiles repo. Example:"
+    echo "  export FLAKE_REF=github:USER/REPO   # or path:/path/to/dotfiles/nixos"
+    exit 1
+  fi
+fi
+
+if [[ "$EUID" -ne 0 ]]; then
+  echo "Run as root (e.g. sudo $0)"
+  exit 1
+fi
+
+read -r -p "Hostname (e.g. my-server): " hostname
+if [[ -z "$hostname" ]]; then
+  echo "Hostname cannot be empty."
+  exit 1
+fi
+
+read -r -p "Target disk [default: /dev/sda]: " disk
+disk="${disk:-/dev/sda}"
+if [[ ! -b "$disk" ]]; then
+  echo "Not a block device: $disk"
+  exit 1
+fi
+
+if [[ -n "${INSTALLER_SYSTEM_CONFIG_FILE:-}" ]] && [[ -f "$INSTALLER_SYSTEM_CONFIG_FILE" ]]; then
+  # Use provided JSON; ensure hostname is set
+  if command -v jq &>/dev/null; then
+    SYSTEM_CONFIG=$(jq --arg h "$hostname" '.networking.hostName = $h' "$INSTALLER_SYSTEM_CONFIG_FILE")
+  else
+    SYSTEM_CONFIG=$(cat "$INSTALLER_SYSTEM_CONFIG_FILE")
+    echo "Warning: jq not found, using file as-is (hostname may not match)."
+  fi
+else
+  SYSTEM_CONFIG='{"networking":{"hostName":"'"$hostname"'"}}'
+fi
+
+echo "Flake:      ${FLAKE_REF}#server-install"
+echo "Disk:       $disk"
+echo "Hostname:   $hostname"
+echo "System config: $SYSTEM_CONFIG"
+read -r -p "Proceed? [y/N] " confirm
+if [[ "${confirm,,}" != "y" && "${confirm,,}" != "yes" ]]; then
+  echo "Aborted."
+  exit 0
+fi
+
+exec nix run github:nix-community/disko/latest#disko-install -- \
+  --flake "${FLAKE_REF}#server-install" \
+  --disk main "$disk" \
+  --system-config "$SYSTEM_CONFIG"