nixos/display-managers/startx: init

[xeji]

Motivation for this change

This defines the startx dummy display manager that allows running X as a normal user.
The X server is started manually from a VT using startx. It is possible to start multiple X sessions from different VTs.

Session startup commands must be provided by the user in ~/.xinitrc, which is NOT automatically generated. This lack of integration with the desktopManager and windowManager settings and other NixOS options is intentional, to keep it simple and give users full control over their X session, independent of system-wide settings.

Here's how I use it with my minimal dwm desktop:

  services.xserver = {
    enable = true;
    displayManager.startx.enable = true;
    desktopManager.default = "none";
    desktopManager.xterm.enable = false;
    windowManager.dwm.enable = true;  # as a convenient way to install the dwm package
  };

A minimal ~/.xinitrc without any extra initialisations may look like:

exec dwm

Things done

• writing this on a NixOS system using it.

---

[xeji]

Combining this with pam-autologin would be a lightweight alternative to our current auto display manager. cc @oxij

[Mic92]

orthogonal to this pr it would be nice to have something similar for wayland based sessions.

[oxij]

Awesome, thanks! I still think we need to merge #46396, though, `lightdm + xmonad` are still broken for me. Will reusing `.xsession` script just work, can I just put `exec .xsession` in `.xinitrc`? Why `displayManager.lightdm.enable = lib.mkForce false;`?

[xeji]

Will reusing .xsession script just work, can I just put exec .xsession in .xinitrc?

Yes. On my system I use home-manager to generate .xsession and do that.

Why displayManager.lightdm.enable = lib.mkForce false;?

lightdm is enabled by default here. I don't like the logic above that line as it's non-modular and don't want to add another display manager to it. That's why I chose mkForce. The default mechanism needs refactoring, but let's leave that for another PR.

[oxij]

lightdm spores everywhere

I see. Running on top of this, and it works perfectly. LGTM. Thanks!

[shazow]

If I'm not mistaken, one issue with this solution that xserver.dpi gets ignored?

[xeji]

If I'm not mistaken, one issue with this solution that xserver.dpi gets ignored?

Yes. You can pass X server options manually to startx: startx -- -dpi 100. The global options are intentonally ignored to give each user control over how they want to run the X server. That's why I call it a dummy display manager.

[shazow]

@xeji Got it, thanks.