Hadoop unknownhostexception when format node

Question

i'm trying to install hadoop on a CentOS server.

I'm using that tutorial.

I stopped on that line:

bin/hadoop namenode –format

12/12/05 15:07:06 INFO namenode.NameNode: STARTUP_MSG: 
/************************************************************
STARTUP_MSG: Starting NameNode
STARTUP_MSG:   host = java.net.UnknownHostException: karpov: karpov
STARTUP_MSG:   args = [-format]
STARTUP_MSG:   version = 1.1.1
STARTUP_MSG:   build = https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1 -r 1411108; compiled by 'hortonfo' on Mon Nov 19 10:48:11 UTC 2012
************************************************************/
Re-format filesystem in /tmp/hadoop-root/dfs/name ? (Y or N) 

Where karpov is my machine name!

On Re-format filesystem in /tmp/hadoop-root/dfs/name ? (Y or N) both Y and N input don't change nothing..
How can i solve? Please help me!

Answer 1

Check /etc/hosts and make sure you have your host added.

Answer 2

May be some special character in your /etc/hosts File.Clean it and write it agin the error must GO.