Most examples on how to run Hive in local mode mention using SET mapred.job.tracker=local. But with YARN this setting no longer has the desired effect, Hive queries are still executed with the M/R framework. Stepping through the Hadoop 23 shims reveals that the decision to split into local mode is driven by different configuration setting:

  @Override
  public boolean isLocalMode(Configuration conf) {
    return "local".equals(conf.get("mapreduce.framework.name"));
  }

Running Hive in localmode is important in debugging, is much easier to attach a remote to the local spawned Java process than to a real cluster, even a local one-node cluster. Thejas has a this short note about running hive in local mode, but following the advise there does not work on YARN clusters like the more recent Hortonworks sandboxes.