本文转自：http://www.aboutyun.com/blog-61-22.html
当我们对hdfs操作的时候，我们可能会碰到如下错误
错误1：权限问题
Exception in thread "main" org.apache.hadoop.security.AccessControlException: org.apache.hadoop.security.AccessControlException: Permission denied: user=,
access=WRITE, inode="":root:supergroup:rwxr-xr-x
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at org.apache.hadoop.ipc.RemoteException.instantiateException(RemoteException.java:95)
at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteException.java:57)
at org.apache.hadoop.hdfs.DFSClient.mkdirs(DFSClient.java:1216)
at org.apache.hadoop.hdfs.DistributedFileSystem.mkdirs(DistributedFileSystem.java:321)
at org.apache.hadoop.fs.FileSystem.mkdirs(FileSystem.java:1126)
at hdfs.hdoopapi.main(hdoopapi.java:19)
Caused by: org.apache.hadoop.ipc.RemoteException: org.apache.hadoop.security.AccessControlException: Permission denied: user=hyj, access=WRITE,
inode="":root:supergroup:rwxr-xr-x
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPermissionChecker.java:199)
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPermissionChecker.java:180)
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermission(FSPermissionChecker.java:128)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkPermission(FSNamesystem.java:5214)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkAncestorAccess(FSNamesystem.java:5188)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInternal(FSNamesystem.java:2060)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:2029)
at org.apache.hadoop.hdfs.server.namenode.NameNode.mkdirs(NameNode.java:817)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:563)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1388)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1384)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1121)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1382)
at org.apache.hadoop.ipc.Client.call(Client.java:1070)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:225)
at sun.proxy.$Proxy1.mkdirs(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:82)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:59)
at sun.proxy.$Proxy1.mkdirs(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient.mkdirs(DFSClient.java:1214)
... 3 more
回答：产生这个错误的原因,是因为HDFS配置文件hdfs-site.xml中，配置了对权限的检查，我们需要把dfs.permissions，value值改为false。
<configuration>
<property>
<name>dfs.replication</name>
<value>1</value>
</property>
<property>
<name>hadoop.tmp.dir</name>
<value>/home/work/hadoop_tmp</value>
</property>
<property>
<name>dfs.permissions</name>
<value>true</value>
</property>
</configuration>
还存在另外一种情况：如下，就是我们对其配置，这个也会产生这个错误。
<configuration>
<property>
<name>dfs.replication</name>
<value>1</value>
</property>
<property>
<name>hadoop.tmp.dir</name>
<value>/home/work/hadoop_tmp</value>
</property>
</configuration>
错误2：端口问题
14/02/24 14:10:45 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 0 time(s).
14/02/24 14:10:47 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 1 time(s).
14/02/24 14:10:49 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 2 time(s).
14/02/24 14:10:51 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 3 time(s).
14/02/24 14:10:53 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 4 time(s).
14/02/24 14:10:55 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 5 time(s).
14/02/24 14:10:57 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 6 time(s).
14/02/24 14:10:59 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 7 time(s).
14/02/24 14:11:01 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 8 time(s).
14/02/24 14:11:03 INFO ipc.Client: Retrying connect to server: aboutyun/192.168.159.10:9000. Already tried 9 time(s).
Exception in thread "main" java.net.ConnectException: Call to aboutyun/192.168.159.10:9000 failed on connection exception: java.net.ConnectException: Connection
refused: no further information
at org.apache.hadoop.ipc.Client.wrapException(Client.java:1099)
at org.apache.hadoop.ipc.Client.call(Client.java:1075)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:225)
at sun.proxy.$Proxy1.getProtocolVersion(Unknown Source)
at org.apache.hadoop.ipc.RPC.getProxy(RPC.java:396)
at org.apache.hadoop.ipc.RPC.getProxy(RPC.java:379)
at org.apache.hadoop.hdfs.DFSClient.createRPCNamenode(DFSClient.java:119)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:238)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:203)
at org.apache.hadoop.hdfs.DistributedFileSystem.initialize(DistributedFileSystem.java:89)
at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:1386)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:66)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:1404)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:254)
at hdfs.hdoopapi.getFileSystem(hdoopapi.java:29)
at hdfs.hdoopapi.main(hdoopapi.java:17)
Caused by: java.net.ConnectException: Connection refused: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:692)
at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:489)
at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:434)
at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:560)
at org.apache.hadoop.ipc.Client$Connection.access$2000(Client.java:184)
at org.apache.hadoop.ipc.Client.getConnection(Client.java:1206)
at org.apache.hadoop.ipc.Client.call(Client.java:1050)
... 14 more
上面是的也是错误，看到很多说是修改配置文件，其实发生这个问题的原因
1.你们之间通信确实产生了问题
2.看一下集群是否已经启动（这个很重要）
试一下start-all.sh或许这个就能解决你的问题。
错误3.Name node处于安全模式：
Exception in thread "main" org.apache.hadoop.ipc.RemoteException: org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create directory /dl. Name node is in safe mode.
The ratio of reported blocks 0.0000 has not reached the threshold 0.9990. Safe mode will be turned off automatically.
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInternal(FSNamesystem.java:2055)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:2029)
at org.apache.hadoop.hdfs.server.namenode.NameNode.mkdirs(NameNode.java:817)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:563)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1388)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1384)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1121)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1382)
at org.apache.hadoop.ipc.Client.call(Client.java:1070)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:225)
at sun.proxy.$Proxy1.mkdirs(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:82)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:59)
at sun.proxy.$Proxy1.mkdirs(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient.mkdirs(DFSClient.java:1214)
at org.apache.hadoop.hdfs.DistributedFileSystem.mkdirs(DistributedFileSystem.java:321)
at org.apache.hadoop.fs.FileSystem.mkdirs(FileSystem.java:1126)
at hdfs.hdoopapi.main(hdoopapi.java:21)