org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot delete /user/admin/grep-temp-610649987. Name node is in safe mode.
The reason is that you can not delete namenode in safe mode
execution:
hdfs dfsadmin -safemode leave
Hadoop run in safe mode by default. Hadoop dfsadmin -safemode by the following parameters, view the status and settings security module is enabled.
enter into safe mode
leave NameNode forced to leave the safe mode
get return information security mode is turned on
wait wait until the end of safe mode
解决办法有二种：
《1》可能运行命令hadoop dfsadmin -safemode leave 离开安全模式，但是每次都需要手动去设置。
《2》通过配置dfs.safemode.threshold.pct的参数。默认情况下是0.9990f。这个配置可以在hdfs-defalut.xml中找到。我们可以把这个参数配置为0，永久关闭安全模式。
在hadoop中的hdfs-site.xml添加如下配置：
<property>
<name>dfs.safemode.threshold.pct</name>
<value>0f</value>
<description>
Specifies the percentage of blocks that should satisfy
the minimal replication requirement defined by dfs.replication.min.
Values less than or equal to 0 mean not to wait for any particular
percentage of blocks before exiting safemode.
Values greater than 1 will make safe mode permanent.
</description>
</property>
重启NameNode就可以了。
