本人最近学习Hadoop，就按照教程搭建了一个Hadoop集群，可是运行的时候，总是遇到一个问题：datanode进程不出现。我查询了很多，试了很多，但是就是无济于事，就仅仅缺少datanode进程。还请高人指教提醒
具体报错如下：
org.apache.hadoop.util.DiskChecker$DiskErrorException: Directory is not readable: /opt/modules/hadoop-2.5.0/data/tmp/dfs/data
at org.apache.hadoop.util.DiskChecker.checkAccessByFileMethods(DiskChecker.java:174)
at org.apache.hadoop.util.DiskChecker.checkDirAccess(DiskChecker.java:160)
at org.apache.hadoop.util.DiskChecker.checkDir(DiskChecker.java:143)
at org.apache.hadoop.hdfs.server.datanode.DataNode$DataNodeDiskChecker.checkDir(DataNode.java:1866)
at org.apache.hadoop.hdfs.server.datanode.DataNode.checkStorageLocations(DataNode.java:1908)
at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1890)
at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1782)
at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1829)
at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:2005)
at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:2029)
2018-04-03 16:09:50,281 FATAL org.apache.hadoop.hdfs.server.datanode.DataNode: Exception in secureMain
java.io.IOException: All directories in dfs.datanode.data.dir are invalid: "/opt/modules/hadoop-2.5.0/data/tmp/dfs/data/"
at org.apache.hadoop.hdfs.server.datanode.DataNode.checkStorageLocations(DataNode.java:1917)
at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1890)
at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1782)
at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1829)
at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:2005)
at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:2029)
目录权限的问题吧，异常说地很清楚了
$ chmod +rw -R /opt/modules/hadoop-2.5.0/data