Nixpkgs: override systemd unit file execstart for bluetooth

[acrylix]

Issue description

hello, I'm trying to disable a bluez plugin by appending an extra option for the execStart command for bluetooth.service, what would be correct way to do this?

I've tried something along the lines of:

  systemd.user.services.bluetooth = {
      description = "Bluetooth Service";
      serviceConfig = {
        Type = "dbus";
        BusName = "org.bluez";
        ExecStart = "${pkgs.bluez}/libexec/bluetooth/bluetoothd --noplugin=avrcp";
      };
      wantedBy = [ "bluetooth.target" ];
  };

but after a rebuild & restart, content of /etc/systemd/system/bluetooth.service still stayed the same.

on non-nix systems I am able to do this via systemctl edit --full bluetooth.service and edit the unit files directly,

any examples is appreciated!

Technical details

- system: `"x86_64-linux"`
 - host os: `Linux 5.1.11, NixOS, 19.09pre183392.83ba5afcc96 (Loris)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.2.2`
 - channels(michael): `"home-manager"`
 - channels(root): `"nixos-19.09pre183392.83ba5afcc96, nixos-hardware"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[jtojnar]

We use systemd overrides for serviceConfig. If the service already has an ExecStart field, you need to clear it first, as per systemd.unit(5).

In Nix, you can achieve that by using a list

  …
  systemd.user.services.bluetooth.serviceConfig.ExecStart = [
    ""
    "${pkgs.bluez}/libexec/bluetooth/bluetoothd --noplugin=avrcp"
  ];
  …

which will result in the expected override.conf file:

…
ExecStart=
ExecStart=/nix/store/…/libexec/bluetooth/bluetoothd --noplugin=avrcp
…

[peterhoeg]

This sadly doesn't work for me, I keep running into either already define
or infinite recursion errors as explained here:
https://stackoverflow.com/questions/50678639/how-to-change-the-serviceconfig-of-a-service-defined-in-nixpkgs-from-configurati

There's also this PR that fixes this: #41446 but I'm stuck whilst waiting
for this to be released..

bluetooth is not a user service - it's a system service, so any kind of overrides should happen on systemd.services.bluetooth and not systemd.user.services.bluetooth.

[4levels]

Hi,

I deleted my comment since I managed to work around it, see here https://github.com/NixOS/nixpkgs/pull/41446

Thans for your quick reply!