anchor.diff:          description = "
             Whether to distribute builds to the machines listed in
             <option>nix.buildMachines</option>.
  +        ";
  +      };
  +
  +      manualNixMachines = mkOption {
  +        default = false;
  +        description = "
  +          Whether to manually manage the list of buildmachines used in distributed 
  +          builds in /etc/nix.machines. 
           ";
         };
   
  
positive.code:           ''
              export PATH=${if config.nix.distributedBuilds then "${pkgs.openssh}/bin:${pkgs.gzip}/bin:" else ""}${pkgs.openssl}/bin:${nix}/bin:$PATH
              ${config.nix.envVars}
              exec \
                nice -n ${builtins.toString config.nix.daemonNiceLevel} \
                ${pkgs.utillinux}/bin/ionice -n ${builtins.toString config.nix.daemonIONiceLevel} \
  
negative.code:         }
        ]
  
        ++ optional (config.nix.distributedBuilds && !config.nix.manualNixMachines)
          { # List of machines for distributed Nix builds in the format expected
            # by build-remote.pl.
            source = pkgs.writeText "nix.machines"
  