anchor.diff:            will refuse to run until you manually rebuild the cache with
             <command>tarsnap --fsck</command>.
   
  -          Note that each individual archive (specified below) has its own cache
  -          directory specified under <literal>cachedir</literal>; this is because
  -          tarsnap locks the cache during backups, meaning multiple services
  -          archives cannot be backed up concurrently or overlap with a shared
  -          cache.
  -
             Set to <literal>null</literal> to disable caching.
           '';
         };
  
positive.code: 
      environment.etc =
        (mapAttrs' (name: cfg: nameValuePair "tarsnap/${name}.conf"
          { text = configFile name cfg;
          }) cfg.archives) //
        (mapAttrs' (name: cfg: nameValuePair "tarsnap/${name}.dirs"
          { text = concatStringsSep " " cfg.directories;
  
negative.code: let
    cfg = config.services.tarsnap;
  
    configFile = cfg: ''
      cachedir ${config.services.tarsnap.cachedir}
      keyfile  ${config.services.tarsnap.keyfile}
      ${optionalString cfg.nodump "nodump"}
      ${optionalString cfg.printStats "print-stats"}
  