说明：突然重启电脑后，重新开启hadoop，启动hive，出现以下错误：
Caused by: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.server.namenode.SafeMo deException): Cannot create directory /tmp/hive/root/9dc0dfcd-a02d-41f3-b524-dc85089e4c3f. Name node is in safe mode.
解决办法：没有关闭安全模式，直接强制离开安全模式就行了
hdfs dfsadmin -safemode leave
