title: "hadoop namenode -format" returns a java.net.UnknownHostException
body: <p>I'm currently learning hadoop and I'm trying to setup a single node test as defined in <a href="http://hadoop.apache.org/common/docs/current/single_node_setup.html" rel="noreferrer">http://hadoop.apache.org/common/docs/current/single_node_setup.html</a></p>
  
  <p>I've configured ssh (I can log without a password).</p>
  
  <p>My server is on our intranet, behind a proxy.</p>
  
  <p>When I'm trying to run </p>
  
  <blockquote>
    <p>bin/hadoop namenode -format</p>
  </blockquote>
  
  <p>I get the following  java.net.UnknownHostException exception:</p>
  
  <pre><code>$ bin/hadoop namenode -format
  11/06/10 15:36:47 INFO namenode.NameNode: STARTUP_MSG: 
  /************************************************************
  STARTUP_MSG: Starting NameNode
  STARTUP_MSG:   host = java.net.UnknownHostException: srv-clc-04.univ-nantes.prive3: srv-clc-04.univ-nantes.prive3
  STARTUP_MSG:   args = [-format]
  STARTUP_MSG:   version = 0.20.203.0
  STARTUP_MSG:   build = http://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.20-security-203 -r 1099333; compiled by 'oom' on Wed May  4 07:57:50 PDT 2011
  ************************************************************/
  Re-format filesystem in /home/lindenb/tmp/HADOOP/dfs/name ? (Y or N) Y
  11/06/10 15:36:50 INFO util.GSet: VM type       = 64-bit
  11/06/10 15:36:50 INFO util.GSet: 2% max memory = 19.1675 MB
  11/06/10 15:36:50 INFO util.GSet: capacity      = 2^21 = 2097152 entries
  11/06/10 15:36:50 INFO util.GSet: recommended=2097152, actual=2097152
  11/06/10 15:36:50 INFO namenode.FSNamesystem: fsOwner=lindenb
  11/06/10 15:36:50 INFO namenode.FSNamesystem: supergroup=supergroup
  11/06/10 15:36:50 INFO namenode.FSNamesystem: isPermissionEnabled=true
  11/06/10 15:36:50 INFO namenode.FSNamesystem: dfs.block.invalidate.limit=100
  11/06/10 15:36:50 INFO namenode.FSNamesystem: isAccessTokenEnabled=false accessKeyUpdateInterval=0 min(s), accessTokenLifetime=0 min(s)
  11/06/10 15:36:50 INFO namenode.NameNode: Caching file names occuring more than 10 times 
  11/06/10 15:36:50 INFO common.Storage: Image file of size 113 saved in 0 seconds.
  11/06/10 15:36:50 INFO common.Storage: Storage directory /home/lindenb/tmp/HADOOP/dfs/name has been successfully formatted.
  11/06/10 15:36:50 INFO namenode.NameNode: SHUTDOWN_MSG: 
  /************************************************************
  SHUTDOWN_MSG: Shutting down NameNode at java.net.UnknownHostException: srv-clc-04.univ-nantes.prive3: srv-clc-04.univ-nantes.prive3
  ************************************************************/
  </code></pre>
  
  <p>After that, hadoop was started</p>
  
  <pre><code>./bin/start-all.sh
  </code></pre>
  
  <p>but there was another new exception when I tried to copy a local file:</p>
  
  <pre><code> bin/hadoop fs  -copyFromLocal ~/file.txt  file.txt
  
  DataStreamer Exception: org.apache.hadoop.ipc.RemoteException: java.io.IOException: File /user/lindenb/file.txt could only be replicated to 0 nodes, instead of 1
      at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:1417)
  </code></pre>
  
  <p>how can I fix this problem please ?</p>
  
  <p>Thanks</p>