code: private void processGeneralOptions(Configuration conf,
        CommandLine line) {
      if (line.hasOption("fs")) {
        FileSystem.setDefaultUri(conf, line.getOptionValue("fs"));
      }
  
      if (line.hasOption("jt")) {
        conf.set("mapred.job.tracker", line.getOptionValue("jt"));
      }
      if (line.hasOption("conf")) {
        String[] values = line.getOptionValues("conf");
        for(String value : values) {
          conf.addResource(new Path(value));
        }
      }
      try {
        if (line.hasOption("libjars")) {
          conf.set("tmpjars", 
                   validateFiles(line.getOptionValue("libjars"), conf));
          //setting libjars in client classpath
          URL[] libjars = getLibJars(conf);
          if(libjars!=null && libjars.length>0) {
            conf.setClassLoader(new URLClassLoader(libjars, conf.getClassLoader()));
            Thread.currentThread().setContextClassLoader(
                new URLClassLoader(libjars, 
                    Thread.currentThread().getContextClassLoader()));
          }
        }
        if (line.hasOption("files")) {
          conf.set("tmpfiles", 
                   validateFiles(line.getOptionValue("files"), conf));
        }
        if (line.hasOption("archives")) {
          conf.set("tmparchives", 
                    validateFiles(line.getOptionValue("archives"), conf));
        }
      } catch (IOException ioe) {
        System.err.println(StringUtils.stringifyException(ioe));
      }
      if (line.hasOption('D')) {
        String[] property = line.getOptionValues('D');
        for(String prop : property) {
          String[] keyval = prop.split("=", 2);
          if (keyval.length == 2) {
            conf.set(keyval[0], keyval[1]);
          }
        }
      }
      conf.setBoolean("mapred.used.genericoptionsparser", true);
    }
docs: Modify configuration according user-specified generic options
  @param conf Configuration to be modified
  @param line User-specified generic options