启动hadoo集群时 namenode没启动。查看日志，报错如下：
java.io.FileNotFoundException: /exapp/hadoop/name/current/VERSION (Permission denied)
at java.io.RandomAccessFile.open(Native Method)
at java.io.RandomAccessFile.<init>(RandomAccessFile.java:216)
at org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.read(Storage.java:220)
at org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.read(Storage.java:216)
at org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:301)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.loadFSImage(FSDirectory.java:87)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.initialize(FSNamesystem.java:311)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:292)
at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:201)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:279)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:956)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:965)
-rw-r--r-- 1 root root 1.0M 2月 4 23:00 edits
-rw-r--r-- 1 root root 533 2月 4 22:59 fsimage
-rw-r--r-- 1 root root 8 2月 4 22:59 fstime
-rw-r--r-- 1 root root 100 2月 4 22:59 VERSION