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Data node EPERM not permitted.
Hi :

I've mounted my own ext4 disk ont /mnt/sdb and chmodded it to 777.

However, when starting the data node:

/etc/init.d/hadoop-hdfs-datanode start

I get the following error in my logs (bottom of this message)

*** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

What is the EPERM error caused by, and how can I reproduce it?  I'm
assuming that, since the directory permissions are recursively set to 777
there shouldnt be a way that this error could occur, unless somewhere
intermittently the directory permissions are being changed by hdfs to the
wrong thing.

*** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

2013-07-06 15:54:13,968 WARN
org.apache.hadoop.hdfs.server.datanode.DataNode: Invalid
dfs.datanode.data.dir /mnt/sdb/hadoop-hdfs/cache/hdfs/dfs/data :
EPERM: Operation not permitted
    at org.apache.hadoop.io.nativeio.NativeIO.chmod(Native Method)
    at
org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:605)
    at
org.apache.hadoop.fs.FilterFileSystem.setPermission(FilterFileSystem.java:439)
    at
org.apache.hadoop.util.DiskChecker.mkdirsWithExistsAndPermissionCheck(DiskChecker.java:138)
    at org.apache.hadoop.util.DiskChecker.checkDir(DiskChecker.java:154)
    at
org.apache.hadoop.hdfs.server.datanode.DataNode.getDataDirsFromURIs(DataNode.java:1659)
    at
org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1638)
    at
org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1575)
    at
org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1598)
    at
org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:1751)
    at
org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1772)

--
Jay Vyas
http://jayunit100.blogspot.com