一、异常现象
启动hadoop时，datanode启动失败，出现如下异常：
2018-03-23 14:39:09,962 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Invalid dfs.datanode.data.dir /ray/hadoop/dfs/data :
ExitCodeException exitCode=1: chmod: changing permissions of `/ray/hadoop/dfs/data': Operation not permitted
at org.apache.hadoop.util.Shell.runCommand(Shell.java:538)
at org.apache.hadoop.util.Shell.run(Shell.java:455)
at org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:715)
at org.apache.hadoop.util.Shell.execCommand(Shell.java:808)
at org.apache.hadoop.util.Shell.execCommand(Shell.java:791)
at org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:656)
at org.apache.hadoop.fs.FilterFileSystem.setPermission(FilterFileSystem.java:490)
at org.apache.hadoop.util.DiskChecker.mkdirsWithExistsAndPermissionCheck(DiskChecker.java:140)
at org.apache.hadoop.util.DiskChecker.checkDir(DiskChecker.java:156)
at org.apache.hadoop.hdfs.server.datanode.DataNode$DataNodeDiskChecker.checkDir(DataNode.java:2239)
at org.apache.hadoop.hdfs.server.datanode.DataNode.checkStorageLocations(DataNode.java:2281)
at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:2263)
at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:2155)
at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:2202)
at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:2378)
at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:2402)
2018-03-23 14:39:09,965 FATAL org.apache.hadoop.hdfs.server.datanode.DataNode: Exception in secureMain
java.io.IOException: All directories in dfs.datanode.data.dir are invalid: "/ray/hadoop/dfs/data/"
at org.apache.hadoop.hdfs.server.datanode.DataNode.checkStorageLocations(DataNode.java:2290)
at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:2263)
at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:2155)
at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:2202)
at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:2378)
at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:2402)
2018-03-23 14:39:09,970 INFO org.apache.hadoop.util.ExitUtil: Exiting with status 1
二、异常原因
原因是 用户 ray 不具备文件夹所属权
三、异常解决
通过命令：
sudo chown -R ray:ray /ray
将文件夹ray及其子文件夹的所属权赋给用户 ray
然后再重新启动即可
四、参考资料
自己奇思妙想