title: HDFS NFS GateWay mount.nfs: Input/output error?
body: <p>HDFS NFS GateWay  mount.nfs: Input/output error?</p>
  
  <p>1.The errors are as follow:</p>
  
  <pre><code>[root@xx sbin]# mount -t nfs -o vers=3,proto=tcp,nolock,noacl,sync localhost:/ /hdfs_y
  mount.nfs: Input/output error
  
  2016-03-10 15:12:06,350 WARN org.apache.hadoop.hdfs.nfs.nfs3.RpcProgramNfs3: Exception
  804 org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hadoop is not allowed to impersonate root
  805 at org.apache.hadoop.ipc.Client.call(Client.java:1475)
  ......
  </code></pre>
  
  <p>2.The process of hadoop, and the user "hadoop" start hadoop.</p>
  
  <pre><code>[root@WEB-W031 sbin]# jps
  6755 Nfs3
  11199 Jps
  6163 Portmap
  7977 SecondaryNameNode
  7720 NameNode
  8217 ResourceManager
  16762 org.eclipse.equinox.launcher_1.3.0.v20130327-1440.jar
  
  [hadoop@WEB-W031 hadoop]$ jps
  6755 Nfs3
  7977 SecondaryNameNode
  7720 NameNode
  8217 ResourceManager
  11239 Jps
  You have new mail in /var/spool/mail/root
  </code></pre>
  
  <p>3.reference：
  <a href="https://hadoop.apache.org/docs/r2.7.2/hadoop-project-dist/hadoop-hdfs/HdfsNfsGateway.html#Allow_mounts_from_unprivileged_clients" rel="nofollow">https://hadoop.apache.org/docs/r2.7.2/hadoop-project-dist/hadoop-hdfs/HdfsNfsGateway.html#Allow_mounts_from_unprivileged_clients</a></p>
  
  <p>Thanks very much!</p>