Why hadoop format give out “java.net.UnknownHostException” exception

Question

I'm learning hadoop and try to set up the environment according to online documents. I've configured the ssh (that ssh localhost won't need a password), configured the "core-site.xml", "hdfs-site.xml", "mapred-site.xml" and "yarn-site.xml" But when I tried "hadoop namenode -format" it gave out "java.net.UnknownHostException" and host = java.net.UnknownHostException:

I've tried to search online help but nearly all are: change the network configuration in etc/hosts. But I'm using hadoop 2.4 and there's no such folder.

Any suggestion?

Thanks!

Answer 1

Well, they are right, you have to change the /etc/hosts file. I assume you have localhost on your hadoop configuration files, so you need to open /etc/hosts as sudo and add the following line:

127.0.0.1 localhost localhost

Answer 2

I found solution which worked for me.

First of all edit your /etc/hostname, write namenode or alias you want to set for namenode then run sudo ifconfig eth0 down&&sudo ifconfig eth0 up and try again.