NixOS

Add the flake as an input and import the module:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    lys-login = {
      url = "github:stubbedev/lys-login";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };
  outputs = {nixpkgs, lys-login, ...}: {
    nixosConfigurations.host = nixpkgs.lib.nixosSystem {
      modules = [
        lys-login.nixosModules.default
        ./configuration.nix
      ];
    };
  };
}

The display manager

enable alone is a working setup. It runs lys-login daemon as display-manager.service, showing the greeter in the lys-wm of lys-login's flake input, and adds the lys-login PAM service, the lys-greeter system user and the state directory, with neither greetd nor cage.

programs.lys-login.greeter = {
  enable = true;
  # Theme it like your desktop: the full lys-shell config schema. The greeter
  # honours styling, login.* and wallpaper.
  settings = {
    styling.appearance = "dark";
    login.background-mode = "color";
    login.background-color = "#1e1e2e";
    login.greeter.cursor-size = 24;
  };
};

settings becomes /etc/lys-shell/config.yaml, and Configuration covers what it holds.

Sessions come from the aggregate NixOS sessions directory, which holds the session files of every installed compositor. The unit does not restart on nixos-rebuild switch, which would end your session; the new one starts at the next boot.

To show the greeter in the lys-wm your desktop runs:

programs.lys-login.greeter.compositorPackage = config.programs.lys-wm.package;

The lock screen

programs.lys-login = {
  enable = true;
  lock.enable = true;
};

enable puts lys-login on the PATH, which greeter.enable does too. lock.enable adds the PAM service the unlock needs. Set login.lock.pam-service in your lys-shell config to match lock.pamService, lys-shell by default.

With lys-splash

With lys-splash as the boot splash, set greeter.splashPackage to it. The greeter then takes the screen from the splash without a blank frame, as GDM does from plymouth: the unit conflicts with lys-splash-quit.service and runs lys-splash deactivate before lys-wm starts, which keeps the splash's frame, and the daemon runs lys-splash quit --retain-splash once the greeter's first frame is presented.

Under greetd

greeter.displayManager = "greetd" runs the greeter under greetd in a cage kiosk instead, with its state owned by greetd's greeter user.

Options

All under programs.lys-login.

Option	Default	What it does
enable	false	lys-login on the PATH.
package	this flake's	The lys-login package.
lock.enable	false	Declares the lock screen's PAM service.
lock.pamService	"lys-shell"	Its name.
greeter.enable	false	The greeter, run by greeter.displayManager.
greeter.displayManager	"lys-login"	lys-login: lys-login daemon on greeter.vt. greetd: greetd with a cage kiosk.
greeter.compositorPackage	lys-login's lys-wm input	The lys-wm the daemon shows the greeter in.
greeter.splashPackage	null	lys-splash, when it is the boot splash.
greeter.vt	1	The VT the daemon runs on.
greeter.settings	{}	Written to /etc/lys-shell/config.yaml when set.
greeter.session.dirs	NixOS sessions dir	Directories scanned for Wayland *.desktop session files.
greeter.session.x11Dirs	NixOS xsessions dir	The same for X11, launched through startx; [] disables them. startx must be on the session's PATH, typically through services.xserver.enable.
greeter.session.command	""	An explicit fallback session, offered as "Custom", and the only entry when the directories yield none.
greeter.session.environment	[]	Extra KEY=value entries for the started session.
greeter.cagePackage	pkgs.cage	Under greetd: the kiosk compositor.
greeter.renderer	"auto"	Under greetd: software puts cage on its pixman renderer and the greeter on the CPU. The display manager takes only auto, as lys-wm falls back to software itself.
greeter.graphicsWrapper	[]	Under greetd: a command prefix around the whole launch, such as a nixGL wrapper. The display manager takes none.

The module refuses to evaluate when no session can be offered, or when renderer or graphicsWrapper are set under the display manager.