lightdm has no session types configured in nixos-unstable

[peti]

I updated by NixOS machine to nixos-unstable @ 4e60699 today, but unfortunately that update broke lightdm. The display manager has lost all configured session types -- most importantly the xterm session type I normally use to log in. As a result, I can no longer log in. Lightdm accepts my passwords, but fails to initialize a session. Logins work fine in the previous NixOS version 3f4144c.

The system log says not much, I'm afraid. I all saw is this:

systemd[1]: display-manager.service: Preparation of eBPF accounting maps failed: Operation not permitted
systemd[1]: Starting X11 Server...
systemd[1]: Started X11 Server.
lightdm[1681]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)
systemd[1]: Stopping X11 Server...
lightdm[1529]: Session pid=1704: Error writing to session: Broken pipe
lightdm[1529]: Session pid=1704: Error writing to session: Broken pipe
lightdm[1529]: Session pid=1704: Error writing to session: Broken pipe
lightdm[1529]: Session pid=1704: Error writing to session: Broken pipe
lightdm[1529]: Session pid=1704: Error writing to session: Broken pipe
lightdm[1529]: Session pid=1704: Error writing to session: Broken pipe
lightdm[1529]: Session pid=1704: Error writing to session: Broken pipe
lightdm[1529]: Session pid=1704: Error writing to session: Broken pipe
display-manager[1529]: Failed to get D-Bus connection
systemd[1]: display-manager.service: Main process exited, code=exited, status=1/FAILURE
systemd[1]: display-manager.service: Failed with result 'exit-code'.
systemd[1]: Stopped X11 Server.
systemd[1]: display-manager.service: Consumed 1.826s CPU time.

[worldofpeace]

most importantly the xterm session type I normally use to log in

xterm was disabled as a default, #67355

perhaps we should do #67355 (comment)

[worldofpeace]

Btw, lightdm keeps its logs at /var/log/lightdm.

[obadz]

Live from London meetup:

Repro:Live from London meetup:

nix-build -E 'let pkgs = import <nixpkgs> {}; in with import <nixpkgs/nixos> {
configuration = {
users.extraUsers.guest.isNormalUser = true;
users.extraUsers.guest.initialHashedPassword = "";
virtualisation.graphics = true;
environment.systemPackages = with pkgs; [ vim python36 ];
services.xserver.enable = true;
services.xserver.displayManager.lightdm.enable = true;
documentation.nixos.enable = false;
}; }; vm' && rm ./nixos.qcow2 && ./result/bin/run-nixos-vm 

Reverting f140dfb indeed brings xterm back in the menu. @adisbladis says we should strive for something better though.

[obadz]

@peti, if you're ok with #68363, let's close this?

[peti]

OK.