SDDM
Simple Desktop Display Manager (SDDM) is a modern display manager for X11 and Wayland sessions.
Installation
SDDM can be enabled as the display manager with these lines.
services.displayManager.sddm = {
enable = true;
# Enables experimental Wayland support
wayland.enable = true;
};
Configuration
Wayland
services.displayManager.sddm = {
enable = true;
wayland = {
enable = true;
# default compositor is "weston", you can optionally change it to kwin
#compositor = "kwin";
};
};
};
Autologin
services.displayManager = {
sddm = {
enable = true;
wayland.enable = true;
};
autoLogin = {
enable = true;
user = "user"; # Replace with the desired user
};
};
Disable/Enable fprint
With fprint enabled on the system, SDDM will expect a fingerprint after entering any password. SDDM does not show any prompt for this and this will time out after some time and SDDM will attempt to use your entered password. If you have your fingerprints enrolled, you can press enter and use your fingerprint reader. You may find additional options for fprint as well as information on enrolling fingerprints on the Fingerprint scanner page.
KWallet cannot be unlocked using fprint.
Enable fprint system wide
You can enable this behavior by enabling fprint.
services.fprintd.enable = true;
Disable fprint for login
Stops SDDM from prompting for fingerprint.
security.pam.services.login.fprintAuth = false;
Troubleshooting
SDDM Hangs after entering password
With fprint enabled, SDDM will expect a fingerprint after entering any password. SDDM is likely waiting for a fingerprint without a prompt. You can disable this behavior by seeing the fprint configuration section of this article.
SDDM does not unlock KWallet on KDE
This may be related to fprint. Using fprint to login cannot unlock KWallet since KWallet unlocks using the same password as your user, and does not support fingerprints to do so.
Session freezes/leads to black screen after logging out
Some Desktop Sessions may rely on logind to terminate themselves (e.g.: UWSM, loginctl, …), but SDDM currently fails at correctly handling signals from logind, leaving it in a limbo state where it can't restart the greeter[1]. If it ever happens, SDDM can be manually restarted by logging into another TTY, and restarting the display-manager.service system service.
However, there are workarounds to avoid doing this altogether.
Killing the session instead of terminating
If you are using loginctl to log out, use the kill-session command instead of the terminate-session. This will force the greeter to restart. Some reports[2] say that uwsm stop may work as well.
Patch SDDM to correctly handle signals from logind
An upstream PR fixing this issue is currently pending review. You can apply it by overriding SDDM to include the PR as a patch:
{ pkgs, ... }:
{
services.displayManager.sddm.package = pkgs.kdePackages.sddm.override {
unwrapped = (
pkgs.kdePackages.sddm.unwrapped.overrideAttrs (old: {
patches = (old.patches or [ ]) ++ [
(pkgs.fetchpatch {
url = "https://patch-diff.githubusercontent.com/raw/sddm/sddm/pull/2103.patch";
hash = "sha256-HxsurSuGJjkGnC8fAiwipadAgcTUhs7n6fQ1SmvMMGc=";
})
];
})
);
};
}
Installing themes
You can install and configure a theme like so
{ pkgs, ... }:
{
services.displayManager.sddm = {
enable = true;
theme = "catppuccin-mocha-mauve";
};
environment.systemPackages = [
(pkgs.catppuccin-sddm.override {
flavor = "mocha";
accent = "mauve";
})
];
}