{
  description = "NixOS definitions for our physical servers";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-23.11";
    nixpkgs-unstable.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    deploy-rs.url = "github:serokell/deploy-rs";
    kubenix = {
      url = "github:hall/kubenix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    disko = {
      url = "github:nix-community/disko";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    agenix = {
      url = "github:ryantm/agenix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    dns = {
      url = "github:kirelagin/dns.nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    microvm = {
      url = "github:astro/microvm.nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs =
    { self, nixpkgs, deploy-rs, disko, agenix, kubenix, nixpkgs-unstable, dns, microvm, ... }:
    let
      system = "x86_64-linux";
      pkgs = nixpkgs.legacyPackages.${system};
      lib = pkgs.lib;
      pkgs-unstable = nixpkgs-unstable.legacyPackages.${system};
      machines = import ./nixos/machines;
      # TODO: Maybe use mergeAttrLists
      mkNixosSystems = systemDef:
        nixpkgs.lib.foldlAttrs
          (acc: name: machine:
            acc // {
              "${name}" = nixpkgs.lib.nixosSystem (systemDef machine);
            })
          { }
          machines;
      mkDeployNodes = nodeDef:
        nixpkgs.lib.foldlAttrs
          (acc: name: machine: acc // { "${name}" = nodeDef machine; })
          { }
          machines;
    in
    {
      devShells.${system}.default = pkgs.mkShell {
        packages = with pkgs; [
          libsecret
          # TODO: using nixos-anywhere from nixos-unstable produces buffer overflow.
          # Related to this issue: https://github.com/nix-community/nixos-anywhere/issues/242
          # Should wait until this is merged in nixos-unstable.
          # pkgs-unstable.nixos-anywhere
          pkgs-unstable.deploy-rs
          openssl
          postgresql_15
          opentofu
          cdrtools
          kubectl
          ansible
        ];
      };

      formatter.${system} = pkgs.nixfmt;

      nixosConfigurations = mkNixosSystems (machine: {
        inherit system;
        specialArgs = { inherit kubenix dns; };
        modules = [
          microvm.nixosModules.host
          machine.nixosModule
          disko.nixosModules.disko
          agenix.nixosModules.default
          ./nixos
          { networking.hostName = machine.name; }
        ];
      });

      deploy = {
        sshUser = "root";
        user = "root";

        nodes = mkDeployNodes (machine: {
          hostname = machine.hostName;
          profiles.system = {
            path = deploy-rs.lib.${system}.activate.nixos
              self.nixosConfigurations.${machine.name};
          };
        });
      };

      checks = builtins.mapAttrs
        (system: deployLib: deployLib.deployChecks self.deploy)
        deploy-rs.lib;

      apps.${system} =
        let
          hostNames = builtins.concatStringsSep " " (builtins.map (host: "\"${host.config.networking.fqdn}\"") (builtins.attrValues self.nixosConfigurations));
        in
        {
          reboot-all-vms =
            let
              reboot-all-vms = pkgs.writeScriptBin "reboot-all-vms" ''
                hostNames=(${hostNames})
                for hostName in ''${hostNames[@]}; do
                  units=$(${pkgs.openssh}/bin/ssh root@$hostName systemctl list-units --all)
                  microvmUnits=$(${pkgs.coreutils}/bin/echo "$units" | ${pkgs.gnugrep}/bin/grep 'microvm@.*\.service' | ${pkgs.gawkInteractive}/bin/awk '{print $1}')
                  if [ -n "$microvmUnits" ]; then
                    for microvmUnit in "$microvmUnits"; do
                      ${pkgs.coreutils}/bin/echo "Restarting $microvmUnit on $hostName"
                      ${pkgs.openssh}/bin/ssh root@$hostName systemctl restart "$microvmUnit"
                    done
                  fi
                done
              '';
            in
            {
              type = "app";
              program = "${reboot-all-vms}/bin/reboot-all-vms";
            };

          reboot-vm =
            let
              reboot-vm = pkgs.writeScriptBin "reboot-vm" ''
                if [ -z "$1" ]; then
                  ${pkgs.coreutils}/bin/echo "Please provide a VM name!"
                  exit 1
                fi

                hostNames=(${hostNames})
                unitName="microvm@$1.service"
                for hostName in ''${hostNames[@]}; do
                  units=$(${pkgs.openssh}/bin/ssh root@$hostName systemctl list-units --all)
                  if [[ "''${units[@]}" =~ "$unitName" ]]; then
                    ${pkgs.coreutils}/bin/echo "Restarting $unitName on $hostName"
                    ${pkgs.openssh}/bin/ssh root@$hostName systemctl restart "$unitName"
                  fi
                done
              '';
            in
            {
              type = "app";
              program = "${reboot-vm}/bin/reboot-vm";
            };
        };
    };
}