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Add a script to automate the host creation via templates
The script scripts/mkHost.sh automates the generation of a new host, based on a template file. This template looks like a .nix file with placeholder \$KEY fields that will be populated dynamically such as name, site, user, etc.
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‎scripts/mkHost.sh‎

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Original file line numberDiff line numberDiff line change
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#! /usr/bin/env bash
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set -euo pipefail
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usage() {
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cat <<'EOF'
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Usage:
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nix run .#mkHost -- <name> <sitename> <username> [--system <x86_64-linux|aarch64-linux>] [--help] [--template <path>] [KEY=VALUE ...]
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Arguments:
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<name> Hostname / machine name (e.g. alfa, bravo, ...)
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<sitename> Logical site / location name (e.g. theta, ...)
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<username> User name for the admin user of the new machine
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Options:
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-s, --system Override detected system (default: based on uname -m)
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Allowed: x86_64-linux, aarch64-linux
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-t, --template Path to a template file to use instead of /etc/nixos/templates/hosts/default.tmpl
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-h, --help Show this help
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Extra template variables:
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Any additional arguments of the form KEY=VALUE after the options will be
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exported to the environment before rendering the template, so they can be
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used as \$KEY placeholders inside the template.
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EOF
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}
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info() {
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printf "\e[1;32m[INFO]\e[0m %s\n" "$1"
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}
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error() {
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printf "\e[1;31m[ERROR]\e[0m %s\n\n" "$1" >&2
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usage >&2
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exit 1
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}
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interaction() {
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printf "\e[1;33m[ACTION]\e[0m %s" "$1"
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}
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prompt() {
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local msg="$1"
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interaction "$msg [Y/n] "
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read -r answer
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case "${answer:-Y}" in
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[Yy]*)
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return 0
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;;
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*)
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return 1
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;;
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esac
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}
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if [[ $# -eq 0 ]]; then
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usage
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exit 0
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fi
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if [[ "${1:-}" == "-h" || "${1:-}" == "--help" ]]; then
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usage
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exit 0
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fi
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ARCH="$(uname -m)"
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case "$ARCH" in
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x86_64)
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SYSTEM="x86_64-linux"
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;;
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aarch64 | arm64)
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SYSTEM="aarch64-linux"
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;;
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*)
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SYSTEM=""
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;;
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esac
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if [[ $# -lt 3 ]]; then
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error "missing required arguments <name> <sitename> <username>."
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fi
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NAME="$1"
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SITE="$2"
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USER="$3"
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shift 3
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if [[ ! "$NAME" =~ ^[a-zA-Z0-9._-]+$ ]]; then
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error "invalid host name '$NAME'.
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Allowed characters: letters, numbers, dot, underscore, dash."
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fi
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if [[ ! "$SITE" =~ ^[a-zA-Z0-9._-]+$ ]]; then
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error "invalid site name '$SITE'.
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Allowed characters: letters, numbers, dot, underscore, dash."
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fi
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if [[ ! "$USER" =~ ^[a-z_][a-z0-9_-]*$ ]]; then
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error "invalid username '$USER'.
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Allowed pattern: ^[a-z_][a-z0-9_-]*$ (like normal Unix usernames)."
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fi
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BASE_DIR="/etc/nixos"
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HOSTS_DIR="$BASE_DIR/hosts"
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TARGET_DIR="${HOSTS_DIR}/${NAME}"
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TEMPLATE_FILE="$BASE_DIR/templates/hosts/default.tmpl"
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EXTRA_VARS=()
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while [[ $# -gt 0 ]]; do
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case "$1" in
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-h | --help)
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usage
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exit 0
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;;
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-s | --system)
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if [[ $# -lt 2 ]]; then
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error "--system requires an argument."
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fi
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SYSTEM="$2"
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case "$SYSTEM" in
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x86_64-linux | aarch64-linux) ;;
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*)
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error "invalid --system value '$SYSTEM'.
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Allowed: x86_64-linux, aarch64-linux"
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;;
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esac
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shift 2
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;;
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-t | --template)
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if [[ $# -lt 2 ]]; then
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error "--template requires a path argument."
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fi
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TEMPLATE_FILE="$2"
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shift 2
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;;
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-* | --*)
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error "unknown option '$1'."
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;;
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*)
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if [[ "$1" == *=* ]]; then
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key="${1%%=*}"
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case "$key" in
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NAME | SITE | USER | ARCH | SYSTEM | STATE_VERSION | BASE_DIR | HOSTS_DIR | TARGET_DIR | TEMPLATE_FILE | TARGET_FILE | EXTRA_VARS | HOST_ID)
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error "extra variable '$key' is reserved and cannot be overridden."
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;;
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esac
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EXTRA_VARS+=("$1")
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shift
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else
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error "unexpected positional argument '$1' after <name> <sitename> <username>."
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fi
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;;
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esac
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done
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if [[ -z "${SYSTEM:-}" ]]; then
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error "unsupported architecture '$ARCH' from uname -m.
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Please specify --system x86_64-linux or aarch64-linux explicitly."
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fi
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if [[ -d "$BASE_DIR" ]]; then
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if [[ ! -d "$HOSTS_DIR" ]]; then
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info "creating host directory '$HOSTS_DIR'..."
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mkdir -p "$HOSTS_DIR"
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fi
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else
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error "this script must be run on a NixOS system (with '$BASE_DIR' available)."
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fi
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if [[ -e "$TARGET_DIR" ]]; then
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error "host directory '$TARGET_DIR' already exists."
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fi
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mkdir -p "$TARGET_DIR"
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if ! command -v nixos-generate-config >/dev/null 2>&1; then
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error "nixos-generate-config not found in PATH.
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This script must be run on a NixOS system (or with nixos-generate-config available)."
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fi
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info "generating hardware configuration for $NAME..."
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nixos-generate-config --show-hardware-config >"${TARGET_DIR}/hardware.nix"
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TARGET_FILE="$TARGET_DIR/default.nix"
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if [[ ! -f "$TEMPLATE_FILE" ]]; then
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error "template file '$TEMPLATE_FILE' not found."
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fi
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STATE_VERSION=
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if [[ -z "$STATE_VERSION" ]]; then
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if command -v nixos-option >/dev/null 2>&1; then
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v="$(nixos-option system.stateVersion 2>/dev/null |
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sed -nE 's/^[[:space:]]*"([^"]+)".*/\1/p' |
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head -n1)"
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if [[ -n "$v" && "$v" != "null" ]]; then
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STATE_VERSION="$v"
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fi
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fi
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fi
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if [[ -z "$STATE_VERSION" ]]; then
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if command -v nixos-version >/dev/null 2>&1; then
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v="$(nixos-version | sed -E 's/^([0-9]+\.[0-9]+).*/\1/')"
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if [[ -n "$v" ]]; then
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STATE_VERSION="$v"
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fi
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fi
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fi
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if [[ -z "$STATE_VERSION" ]]; then
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error "Could not determine system.stateVersion automatically.
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Please set it manually or ensure nixos-option / nixos-version are available."
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fi
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HOST_ID="$(hexdump -n 4 -e '/4 "%08x"' /dev/urandom | tr 'A-F' 'a-f')"
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for kv in "${EXTRA_VARS[@]}"; do
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export "$kv"
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done
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export NAME SITE USER STATE_VERSION HOST_ID
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if [[ "$TEMPLATE_FILE" == "$BASE_DIR/templates/hosts/default.tmpl" ]]; then
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info "generating configuration for $NAME from default template..."
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else
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info "generating configuration for $NAME from template '$TEMPLATE_FILE'..."
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fi
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envsubst <"$TEMPLATE_FILE" >"$TARGET_FILE"
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if prompt "successfully generated a new config for $NAME. Do you want to edit it now?"; then
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"${EDITOR:-vi}" "$TARGET_FILE"
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else
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info "skipping edit."
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fi

‎hosts/templates/default-configuration.nix‎ renamed to ‎templates/hosts/default.tmpl‎

Lines changed: 17 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -10,39 +10,32 @@ let
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in
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{
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imports = [
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# The hardware-dependent options
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./hardware-configuration.nix
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# All (shared/non-specific) users
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../../users/lukas.nix
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# All custom modules
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# The hardware-dependent options:
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./hardware.nix
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# Common settings thath apply to all machines:
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../common.nix
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# Deployment-site specific options:
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../../sites/"$SITE".nix
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# The users for this system:
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../../users/"$USER".nix
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# The custom modules:
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# TODO: Import any custom modules here.
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# Any third-party modules or flakes:
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# TODO: Import any thrid-party flakes here such as:
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# inputs.sops-nix.nixosModules.sops
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];
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nix.settings.experimental-features = [
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"nix-command"
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"flakes"
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];
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25-
time.timeZone = "Europe/Berlin";
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2728
boot = {
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loader.grub = {
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enable = true;
30-
zfsSupport = true;
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efiSupport = true;
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efiInstallAsRemovable = true;
33-
mirroredBoots = [
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{
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devices = [ "nodev" ];
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path = "/boot";
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}
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];
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};
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zfs.extraPools = [ "zpool" ];
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};
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networking = {
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hostName = "<HOSTNAME>";
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hostId = "<SOME_RANDOM_8_CHARS>";
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hostName = "$NAME";
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hostId = "$HOSTID";
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networkmanager.enable = true;
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useDHCP = true;
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nameservers = [
@@ -57,7 +50,6 @@ in
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search = [ "tabby-crocodile.ts.net" ];
5851
};
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60-
i18n.defaultLocale = "en_US.UTF-8";
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console = {
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font = "Lat2-Terminus16";
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useXkbConfig = true;
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PasswordAuthentication = true;
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KbdInteractiveAuthentication = true;
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PermitRootLogin = "no";
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AllowUsers = [ "lukas" ];
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AllowUsers = [ "$USER" ];
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};
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};
84-
fail2ban = {
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enable = true;
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};
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envfs.enable = true;
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tailscale.enable = true;
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};
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neovim.defaultEditor = true;
9584
};
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97-
system.stateVersion = "25.05";
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system.stateVersion = "$SYSTEM_VERSION";
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}

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