Greeter

The Shady greeter is the login screen greetd shows before anyone logs in: Shady itself, running the Afterglow sky and sea, with a login card from shady-shell in front of it. Logging in carries on into a Shady session under the same sky.

Using it

On NixOS, with the flake’s module:

programs.shady.enable = true;
programs.shady.greeter.enable = true;

This enables greetd with shady-greeter as its default session, run as the greeter user, and keeps the last user and session in /var/lib/shady-greeter/last. programs.shady.greeter.hint adds a line under the card, for example how to log in to a live system.

Elsewhere, point greetd at the installed script:

[default_session]
command = "shady-greeter"
user = "greeter"

Type the password and press Enter. Up and Down pick the user, Tab the session, Escape clears the field. Restart and Shut down run systemctl reboot / systemctl poweroff.

Pieces


`shady-greeter` (`data/shady-greeter.in`)	starts Shady with the greeter’s config, `shady-shell` as its only client, and logs to the journal (`journalctl -t shady-greeter`)
`greeter/config.lua`	the compositor: Afterglow’s sky plugin and no shortcuts at all, so nothing on the login screen can start programs (even the default Escape-to-quit is unbound)
`greeter/init.lua`	frosted glass behind the card and Afterglow’s camera
`greeter/shell.lua`	the login card: a `persistent` popup with exclusive keyboard focus
`greeter/src/greetd.c`	the `greetd` shell plugin: speaks greetd’s IPC and lists accounts and sessions

The card asks the plugin to authenticate; when greetd accepts the chosen session the plugin asks the compositor to quit over its IPC socket, and greetd starts the session once the greeter has exited.

The greetd plugin

Values (read with shell.value):

Value
`greetd.users`	one `name\tdisplay name` line per regular account (UID 1000–59999 with a login shell)
`greetd.sessions`	one `name\tid` line per `.desktop` file in the session directories
`greetd.state`	`idle`, `busy`, `prompt`, `done` or `error`
`greetd.prompt`, `greetd.secret`	PAM’s question while in `prompt`, and `"1"` when the answer should be hidden
`greetd.message`, `greetd.message_kind`	the last info or error text (`info` / `error`)
`greetd.last_user`, `greetd.last_session`	the previous login

Actions (run with shell.action):

Action
`greetd.session(id)`	the session to start once authenticated
`greetd.login(user)`	start authenticating `user`
`greetd.respond(text)`	answer PAM; an answer given before the question arrives is kept for it, so `login` and `respond` together need a single Enter
`greetd.cancel()`	give up the current attempt

Sessions come from the colon-separated directories in SHADY_GREETER_SESSIONS (by default /run/current-system/sw/share/wayland-sessions, /usr/local/share/wayland-sessions and /usr/share/wayland-sessions) and are started as sh -c "<Exec>". The last login is stored in SHADY_GREETER_STATE, or $XDG_STATE_HOME/shady-greeter/last.

Trying it

SHADY_GREETER_DEMO=1 replaces greetd with a fake that accepts any non-empty password, so the greeter can run nested or headless:

SHADY_GREETER_DEMO=1 WLR_BACKENDS=wayland shady-greeter

nix build .#checks.x86_64-linux.greeter boots a VM to the greeter, fails a login, logs in and checks that the user’s Shady session starts.