anchor.diff:  
     config = mkIf config.services.nfsKernel.enable {
   
  +    assertions = singleton
  +      { assertion = config.services.portmap.enable;
  +        message = "Please enable portmap (services.portmap.enable) to use nfs-kernel.";
  +      };
  +
       environment.etc = singleton
         { source = exports;
           target = "exports";
  
positive.code: 
          description = "Kernel NFS server";
  
          startOn = "started nfs-kernel-exports";
          stopOn = "stopping nfs-kernel-exports";
  
          exec = "${pkgs.nfsUtils}/sbin/rpc.nfsd ${if cfg.hostName != null then "-H ${cfg.hostName}" else ""} ${builtins.toString cfg.nproc}";
  
negative.code: 
          description = "Kernel NFS server - mount daemon";
  
          startOn = "started nfs-kernel-nfsd and started portmap";
          stopOn = "stopping nfs-kernel-exports";
  
          exec = "${pkgs.nfsUtils}/sbin/rpc.mountd -F -f ${exports}";
  