Systemd user service not started

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1

I’m trying out nixos currently using the WSL2 nixos distro at https://github.com/Trundle/NixOS-WSL

It seems to be working mostly flawlessly, however I appear to not have the systemd user service:

nixos@nixos ~ [1]> ps aux | grep systemd
root         1  0.0  0.0  25456 11096 ?        Ss   14:20   0:00 systemd
root        21  0.0  0.0  36996 12568 ?        Ss   14:20   0:00 /nix/store/q6ylicsava582g55mdx0788yg2fib7js-systemd-246.6/lib/systemd/systemd-journald
root        51  0.0  0.0  16568  5776 ?        Ss   14:20   0:00 /nix/store/q6ylicsava582g55mdx0788yg2fib7js-systemd-246.6/lib/systemd/systemd-logind
message+    53  0.0  0.0   6368  3680 ?        Ss   14:20   0:00 /nix/store/4013xmv3pjddrdgb6vkncb4iqlyij8pq-dbus-1.12.20/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
nixos    16197  0.0  0.0 223440  2364 pts/0    S+   18:47   0:00 /nix/store/3mx947xcmsyk79izqc8ifv31qafp80pc-gnugrep-3.6/bin/grep --color=auto systemd

This means that whenever I (or specifically lorri) try to interact with it, the command will fail:

nixos@nixos ~> systemctl status --user
Failed to connect to bus: No such file or directory

afaik I need somehow to start the user systemdm process. According to the Arch wiki this is meant to be done by pam, however I gather that in nixos pam is difficult and normally managed by a login/display manager (which isn’t in the WSL version…).

Relevant files:

nixos@nixos ~ [1]> cat /etc/nixos/configuration.nix
{ lib, pkgs, config, modulesPath, ... }:

with lib;
let
  defaultUser = "nixos";
  syschdemd = import ./syschdemd.nix { inherit lib pkgs config defaultUser; };
in
{
  imports = [
    "${modulesPath}/profiles/minimal.nix"
  ];

  # WSL is closer to a container than anything else
  boot.isContainer = true;

  environment.etc.hosts.enable = false;
  environment.etc."resolv.conf".enable = false;

  networking.dhcpcd.enable = false;

  users.users.${defaultUser} = {
    isNormalUser = true;
    extraGroups = [ "wheel" ];
  };

  users.users.root = {
    shell = "${syschdemd}/bin/syschdemd";
    # Otherwise WSL fails to login as root with "initgroups failed 5"
    extraGroups = [ "root" ];
  };

  security.sudo.wheelNeedsPassword = false;

  # Disable systemd units that don't make sense on WSL
  systemd.services."serial-getty@ttyS0".enable = false;
  systemd.services."serial-getty@hvc0".enable = false;
  systemd.services."getty@tty1".enable = false;
  systemd.services."autovt@".enable = false;

  systemd.services.firewall.enable = false;
  systemd.services.systemd-resolved.enable = false;
  systemd.services.systemd-udevd.enable = false;

  # Don't allow emergency mode, because we don't have a console.
  systemd.enableEmergencyMode = false;

  # Enable DBUS
  services.dbus.enable = true;

  nix.extraOptions = ''
    keep-outputs = true
    keep-derivations = true
  '';
1 Like
2

WSL doesn’t support systemd properly.

Systemd strictly requires to be started as PID 1, and WSL starts it’s own process manager there to be able to do it’s magic.

3

The repo I linked to appears to have hacked around this by starting systemd in its own process id space, which they are claiming should fix the problem.

I was thinking that this was in the NixOS layer since it is a user level problem of systemd --user not starting (presumably because there isn’t a proper login manager).

However I most certainly can be wrong about this.

(I’ve opened an issue on that repo to look into this as well)