@afayaz-feral any input?

@mdiluz are you still involved in gamemode, any comments?

I am, I'll chase up with some contacts at Feral. Might be worth explaining why this is needed though.

I can see the merit in having a gamemode group, thanks for adding this.

Thanks everyone. To elaborate on the reason why I think this is a good idea:

AFAICT gamemode manages sysfs entries, where most of the setters (cpu_gov, amdgpu dpm) require root permissions. Using root isn't particularly good, since it exposes much larger surface for misuse or abuse. To avoid that, we add a dedicated group, annotate respective entries and ultimately tighten the scope.

On NixOS, system configuration is usually handled separately from packaging, and the package fails to build with this change: NixOS/nixpkgs#182511.

PermissionError: [Errno 13] Permission denied: '/nix/store/fi2ksazpsqkvspqf36ivlp5ghpxbfm9i-systemd-250.4/lib/sysusers.d'
FAILED: meson-install
/nix/store/1dbfsvzd4i8kdc3yb081gpfddlb80858-meson-0.61.2/bin/meson install --no-rebuild
ninja: build stopped: subcommand failed.

1. Should a flag be added to meson_options.txt to make this optional?
2. Don't the polkit policies already let you run cpugovctl & gpuclockctl as a non-root user? Where is this group used, and how does it differ than what can be specified for with-pam-group?

AFAICT the file must be installed in pkgconfig_systemd.get_pkgconfig_variable('sysusersdir') in order for systemd to pick it up.

I don't know much about the working of NixOS, but it does sound alarming to *NOT use the default config provided by upstream. Nevertheless - feel free to add a meson toggle to disable it. There's systemd-user-unit-dir in there already.

Nix in general supports shipping default configs provided from upstream, as long as the package installs to the $out directory specified in the build (eg. $out/share/systemd/user/gamemoded.service). Whether or not those files are actually used though depends on how the system modules are set up in NixOS.

The problem here is that pkgconfig_systemd.get_pkgconfig_variable('sysusersdir') returns a path that doesn't actually exist and isn't in $out (/nix/store/fi2ksazpsqkvspqf36ivlp5ghpxbfm9i-systemd-250.4/lib/sysusers.d, the parent lib directory does exist), and there's no way to configure this, which is why the build fails.

I think this is because the Nix build of systemd uses -Dsysusers=false: https://github.com/NixOS/nixpkgs/blob/22.05/pkgs/os-specific/linux/systemd/default.nix#L453

Yes that was fairly obvious by the Permission denied message itself. What I'm saying is that, systemd modules (like sysusers but not limited to) will look into the folder specified in systemd.pc.

If the files are *not installed in that location, then the module will not work as expected.

It sounds to me that if a feature (again sysusers or otherwise) is disabled, then the respective path should either be a) unset in the systemd.pc or b) pointing to special location that will not cause issues.

Either way, as mentioned originally feel free to add meson toggle if that makes sense for NixOS.