I am trying to create a 2-node Hadoop cluster, following this guide. The one node is my Ubuntu laptop and the slave node, the 2nd one, is a virtualbox that also runs Ubuntu.

I am doing in the master node:

gsamaras@gsamaras:/home/hadoopuser/hadoop/sbin$ sudo ./start-dfs.sh
16/01/23 04:46:16 WARN hdfs.DFSUtil: Namenode for null remains unresolved for ID null.  Check your hdfs-site.xml file to ensure namenodes are configured properly.
Starting namenodes on [master]
master: ssh: Could not resolve hostname master: Name or service not known
root@localhost's password: 
root@localhost's password: localhost: Permission denied, please try again.

If now I edit my /etc/hosts/ file to this:   localhost   gsamaras   slave-1   master   // should I have this?

the warning will leave, but I will still get a "permission denied". This question is exactly the same with mine's, but the answer did not help much. Any ideas please?

  • Do sudo bash start-dfs.sh. – Raphael Jan 23 '16 at 3:46
  • Same behavior @Raphael – gsamaras Jan 23 '16 at 15:34

Try to give permission to your script file:

$ sudo chmod +x start-dfs.sh

Then execute.

$ sudo bash start-dfs.sh
  • What about /etc/hosts/, how should I have it? I am getting a sudo: +x: command not found. I asked a question about it here: askubuntu.com/questions/724681/sudo-x-command-not-found – gsamaras Jan 23 '16 at 15:47
  • That worked sudo chmod +x start-dfs.sh, but I am getting the same result, permission denied. – gsamaras Jan 23 '16 at 16:04
  • 1
    Solution: Go to sshd_config, change PermitRootLogin without-password -> PermitRootLogin yes and do an ssh restart. – gsamaras Jan 23 '16 at 16:35

I am able to resolve the issue using below commands.

The following commands are used for generating a key value pair using SSH. Copy the public keys form id_rsa.pub to authorized_keys, and provide the owner with read and write permissions to authorized_keys file respectively.

$ ssh-keygen -t rsa 
$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys 
$ chmod 0600 ~/.ssh/authorized_keys 

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