nixos/nfs: `nproc` setting not being applied

[gtebbutt]

Nixpkgs version

• Stable (25.05)

Describe the bug

The setting services.nfs.server.nproc doesn't appear to be applied if set - it's mapped to a setting nfsd.threads in https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/tasks/filesystems/nfs.nix#L20, but the value is not written to /etc/nfs.conf on rebuild, and /proc/fs/nfsd/threads still shows the default value of 8 even after reboot.

Other settings in that block apply correctly (e.g. services.nfs.server.hostName, which correctly writes a host setting under [nfsd] in /etc/nfs.conf), and it looks like server.nproc is the only one that is not prefixed with // in the module code.

Writing the setting directly with services.nfs.settings.nfsd.threads works as expected, so can be used instead of services.nfs.server.nproc.

Steps to reproduce

• Set at least one value in services.nfs.settings, e.g. services.nfs.settings.nfsd.vers3 = false;
• Set a non-default value for services.nfs.server.nproc, e.g. services.nfs.server.nproc = 32;
• Rebuild, and check whether the values in /etc/nfs.conf and /proc/fs/nfsd/threads have changed

Expected behaviour

Changing the value sets threads in /etc/nfs.conf

Screenshots

No response

Relevant log output

Additional context

No response

System metadata

• system: "x86_64-linux"
• host os: Linux 6.12.50, NixOS, 25.05 (Warbler), 25.05.20251004.3bcc93c
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.28.5
• nixpkgs: /nix/store/px86fbsnq65agwvrxnylrxnxp6bpcl76-source

Notify maintainers

---

Note for maintainers: Please tag this issue in your pull request description. (i.e. Resolves #ISSUE.)

I assert that this issue is relevant for Nixpkgs

• I assert that this is a bug and not a support request.
• I assert that this is not a duplicate of an existing issue.
• I assert that I have read the NixOS Code of Conduct and agree to abide by it.

Is this issue important to you?

Add a 👍 reaction to issues you find important.