Trouble getting the NixOS module to run

[Macj332]

Hello,

I just started setting up ncps on a mini PC that I have and I am having difficulty getting ncps to start.
Below is are the messages I am seeing after following the troubleshooting commands from the docs.

Jan 18 19:28:41 melchior-1 systemd[1]: Starting ncps binary cache proxy service...
Jan 18 19:28:41 melchior-1 ncps-pre-start[2847]: Error: no migration files found
Jan 18 19:28:41 melchior-1 systemd[1]: ncps.service: Control process exited, code=exited, status=2/INVALIDARGUMENT
Jan 18 19:28:41 melchior-1 systemd[1]: ncps.service: Failed with result 'exit-code'.
Jan 18 19:28:41 melchior-1 systemd[1]: Failed to start ncps binary cache proxy service.
Jan 18 19:28:41 melchior-1 systemd[1]: ncps.service: Scheduled restart job, restart counter is at 1.

My config for ncps is pretty much copy and pasted from the docs website.
I do not have my NixOS config public but the relevant module is as follows:

services.ncps = {
    enable = true;
    cache = {
      hostName = "melchior-1";
      maxSize = "150G";
      lru.schedule = "0 2 * * *";  # Daily at 2 AM
    };
    upstream = {
      caches = [
        "https://cache.nixos.org"
      ];
      publicKeys = [
        "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
      ];
    };
  };

I have not seen any mention of migration files in the docs so I am unsure where to go from here.
I did try running the database troubleshooting commands but it says that dbmate is not a command.

I am fairly new to Nix so I apologize if I am missing something obvious.

Thank you for your time.

Edit:
I should probably mention that my system is using flakes and nixpkgs-unstable.
I updated my flake just a few hours ago so it should be as up-to-date as can be.

[dosubot[bot]]

Hi @Macj332! I'm Dosu and I’m helping the ncps team.

The error about missing migration files usually means ncps expects to find database migration scripts but can't locate them. Migration files are used to set up or update the application's database schema. In the context of ncps, there’s no documentation indicating you need to manually provide these files or run dbmate (a database migration tool), and dbmate isn't mentioned as a requirement for normal operation.

Your configuration looks correct for basic usage, but one thing to check is whether you need to explicitly set the local cache storage path. The docs indicate you should specify a path using the cache.storage.local option, like this:

services.ncps = {
  enable = true;
  cache = {
    hostName = "melchior-1";
    maxSize = "150G";
    lru.schedule = "0 2 * * *";
    storage.local = "/var/lib/ncps";
  };
  upstream = {
    caches = [ "https://cache.nixos.org" ];
    publicKeys = [ "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=" ];
  };
};

If cache.storage.local is missing, ncps might not know where to store its data, which could lead to errors like the one you’re seeing. Make sure the directory exists and is writable by the ncps service user. You can find more about this option in the documentation.

After updating your config, run sudo nixos-rebuild switch and restart the service. If the error persists, check the permissions on the storage directory and the full logs for any additional clues.

You don’t need to install or run dbmate yourself—if ncps needs database migrations, the module or service should handle it internally. If you still see migration errors after setting the storage path, there may be a packaging or module issue.

To reply, just mention @dosu.

---

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[Macj332]

storage.local is not a valid configuration option.
Setting this option causes nixos to not build.

There is a services.ncps.cache.dataPath option but this should default to the option show in the documentation /var/lib/ncps.
Setting this option manually to /var/lib/ncps does not fix the issue.

[dosubot[bot]]

The NixOS module for ncps is currently out of sync with the latest upstream changes: it only supports the deprecated services.ncps.cache.dataPath option, while recent versions of ncps expect configuration via cache.storage.local instead. This mismatch can cause errors like "no migration files found" because the service may be looking for migration files or data in a location or format that isn't set up by the module. Setting dataPath manually won't fix this, and using storage.local directly in the module isn't supported and will fail to build. More details on the flag changes are in the documentation.

As a workaround, you could check which version of ncps is being installed and try downgrading to a version that matches the module's expectations, or run ncps manually with a YAML config using cache.storage.local to confirm the binary itself works. This is ultimately a packaging/module bug that needs to be resolved to support the new configuration style.

To reply, just mention @dosu.

---

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[Macj332]

I guess I will wait for the package to be fixed then.

As an additional question, is it possible to disable the Anonymous Analytics Reporting in the NixOS module?
I only see instructions on how to disable this when using docker or helm.

[kalbasit]

@Macj332 As I mentioned in #612, this proves to me that your using NixOS modules from release-25.11 but packages (including ncps) from 25.11. Can you try the options I provided in #612 (comment)?