documentation leaves me confused

[tcurdt]

The goal is deploy from aarch64-darwin to x86_64-linux and aarch64-linux.

But I am absolute lost about when it comes to the meta section.
Error messages and documentation seem to suggest something along the lines of

      colmena = {
        meta = {
          nixpkgs = import nixpkgs-stable {
            system = "x86_64-linux";
            overlays = [];
          };
        };

But I don't understand why I would need to specify the nixpkgs in the meta section - and even more so the system.
Both are already declared in the nixosConfigurations. And why would all deployments share the same meta?

But now it gets even more interesting: How do select the nixosConfiguration?
The docs have an example like this:

      host-a = { name, nodes, pkgs, ... }: {
        boot.isContainer = true;
        time.timeZone = nodes.host-b.config.time.timeZone;
      };
      host-b = {
        deployment = {
          targetHost = "somehost.tld";
          targetPort = 1234;
          targetUser = "luser";
        };
        boot.isContainer = true;
        time.timeZone = "America/Los_Angeles";
      };

But that is missing a reference to what should get deployed 🤷‍♂️

I tried this:

        utm-arm = import self.nixosConfigurations.utm-arm {
          deployment = {
            tags = [ "vm" ];
            keys = {
              foo = {
                text = "text";
              };
            };
            targetHost = "192.168.78.7";
            targetUser = "root";
          };
        };

but it seems like that's not the way either.

It would be great to have some real-world example to look at.

[tcurdt]

The full flake is here FWIW

https://github.com/tcurdt/nixcfg/blob/main/flake.nix

[tcurdt]

Digging some more I assume it should be something along the lines of this?
Still not correct but probably closer.

      colmena = {
        meta = {
          nixpkgs = import nixpkgs-stable {
            system = "aarch64-darwin";
          };
        };

        utm-arm = {
          deployment = {
            targetHost = "192.168.78.7";
            targetUser = "root";
          };
          imports = [ self.nixosConfigurations.utm-arm ];
          # imports = [ ./machines/utm-arm.nix ];
        };

[tcurdt]

I got it working now like this

      colmena = {
        meta = {
          nixpkgs = import nixpkgs-stable {
            system = "aarch64-darwin";
          };
          specialArgs = { inherit inputs; };
        };

        utm-arm = {
          deployment = {
            targetHost = "192.168.78.7";
            targetUser = "root";
          };
          imports = [ ./machines/utm-arm.nix ];
        };

but the meta section is still a mystery to me.

[justinas]

Colmena is not flakes-first or flakes-mandatory, hence it takes only NixOS configurations modules (as seen in your last example imports = [ ./machines/utm-arm.nix ];), not an instantiated nixpkgs.lib.nixosSystem which you might have in flakes. So meta.nixpkgs needs to be specified, since otherwise Colmena has no idea what nixpkgs to evaluate with.

See also #60 for ways to integrate flake nixosConfigurations outputs with Colmena.

[justinas]

To expand on your core issue (how to deploy from x86_64 to aarch64), it should be fine setting meta.nixpkgs to a nixpkgs import with the system of your machine, and then specifying nixpkgs.system or nixpkgs.hostPlatform (this one is set automatically nowadays by nixos-generate-config in hardware-configuration.nix) inside the aarch64 machine's configuration. I've used this pattern in the past, although on a flakeless setup.