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:         mkdir -p -m 0700 ${cfg.cachedir}
          chown root:root ${cfg.cachedir}
          chmod 0700 ${cfg.cachedir}
          DIRS=`cat /etc/tarsnap/$1.dirs`
          exec tarsnap --configfile /etc/tarsnap/$1.conf -c -f $1-$(date +"%Y%m%d%H%M%S") $DIRS
        '';
  
negative.code: let
    cfg = config.services.tarsnap;
  
    configFile = name: cfg: ''
      cachedir ${config.services.tarsnap.cachedir}/${name}
      keyfile  ${config.services.tarsnap.keyfile}
      ${optionalString cfg.nodump "nodump"}
      ${optionalString cfg.printStats "print-stats"}
  