anchor.diff:  
           script =
             ''
  +            # Ensure that this job is restarted when fstab changed:
  +            # ${fstab}
               exec > /dev/console 2>&1
               echo "mounting filesystems..."
               ${pkgs.mountall}/sbin/mountall
  
positive.code: 
  with pkgs.lib;
  
  {
  
    ###### interface
  
negative.code:       ++ config.system.fsPackages;
  
      environment.etc = singleton
        { source = fstab;
          target = "fstab";
        };
  
  