nixos/bin/auto-update-nixos

#!/usr/bin/env bash
# Wrapper script for nixos-rebuild

# Configuration parameters
operation="switch"                              # The nixos-rebuild operation to use
hostname=$(/run/current-system/sw/bin/hostname) # The name of the host to build
flakeDir="${FLAKE_DIR}"                         # Path to the flake file (and optionally the hostname). Defaults to the FLAKE_DIR environment variable.
update=false                                    # Whether to update flake.lock (false by default)
user=$(/run/current-system/sw/bin/whoami)       # Which user account to use for git commands (defaults to whoever called the script)
reboot=false
remote=false
remainingArgs=""                                # All remaining arguments that haven't yet been processed (will be passed to nixos-rebuild)

function usage() {
	echo "nixos-rebuild Operations Script (NOS) updates your system and your flake.lock file by pulling the latest versions."
	echo ""
	echo "Running the script with no parameters performs the following operations:"
	echo "  1. Pull the latest version of the config"
	echo "  2. Update your flake.lock file"
	echo "  3. Commit any changes back to the repository"
	echo "  4. Run 'nixos-rebuild switch'."
	echo ""
	echo "Advanced usage: nixos-upgrade-script.sh [-o|--operation operation] [-f|--flake path-to-flake] [extra nixos-rebuild parameters]"
	echo "Options:"
	echo " -h, --help                 Show this help screen."
	echo " -o, --operation            The nixos-rebuild operation to perform."
	echo " -f, --flake <path>         The path to your flake.nix file (and optionally, the hostname to build)."
	echo " -U, --update               Update and commit flake.lock."
	echo " -R, --build-host <user@host>   Build on remote host."
	echo " -r, --reboot               Reboots system is there is a kernel or init update"
	echo " -u, --user                 Which user account to run git commands under."
	echo ""
	exit 2
}

# Argument processing logic shamelessly stolen from https://stackoverflow.com/questions/192249/how-do-i-parse-command-line-arguments-in-bash
POSITIONAL_ARGS=()
while [[ $# -gt 0 ]]; do
  case "$1" in
	--flake|-f)
		flakeDir="$2"
		shift
		shift
		;;
	--update|--upgrade|-U)
		update=true
		shift
		;;
	--reboot|-r)
		reboot=true
		shift
		;;
	--build-host|-R)
		remote=true
		host="$2"
		shift
		shift
		;;
	--operation|-o)
		operation="$2"
		shift
		shift
		;;
	--user|-u)
		user="$2"
		shift
		shift
		;;
	--help|-h)
		usage
		exit 0
		;;
	*)
		POSITIONAL_ARGS+=("$1") # save positional arg
		shift
		;;
	esac
done
remainingArgs=${POSITIONAL_ARGS[@]}
set -- "${POSITIONAL_ARGS[@]}" # restore positional parameters

if [ -z "${flakeDir}" ]; then
	echo "Flake directory not specified. Use '--flake <path>' or set \$FLAKE_DIR."
	exit 1
fi

cd $flakeDir

current_branch=$(git branch --show-current)
[ "$current_branch" != "master" ] && echo "Not on master branch. Aborting auto-update" && exit 0

echo "Pulling the latest version of the repository..."
/run/wrappers/bin/sudo -u $user git stash
/run/wrappers/bin/sudo -u $user git pull

/run/wrappers/bin/sudo -u $user nix flake update --commit-lock-file && /run/wrappers/bin/sudo -u $user git push

options="--flake $flakeDir $remainingArgs --use-remote-sudo"

echo "Running this operation: nixos-rebuild $operation $options"

/run/wrappers/bin/sudo -u root /run/current-system/sw/bin/nixos-rebuild $operation $options

echo "Checking if reboot is necessary"
reboot_diff=$(diff <(readlink /run/booted-system/{initrd,kernel,kernel-modules}) <(readlink /nix/var/nix/profiles/system/{initrd,kernel,kernel-modules}))
if [ -n "$reboot_diff" ] && [ $reboot == true ]; then
  echo "System requires a reboot. Rebooting now..."
  reboot
else
  echo "No reboot necessary."
  echo "Update complete."
  exit 0
fi
echo "Update complete."
exit 0