I tried the following:
*
hadoop-1.1.1/docs/single_node_setup.html
in order for passphraseless ssh to work, the below is not sufficient:
Setup passphraseless ssh

Now check that you can ssh to the localhost without a passphrase:
$ ssh localhost

If you cannot ssh to localhost without a passphrase, execute the following
commands:
$ ssh-keygen -t dsa -P '' -f ~/.ssh/id_dsa
$ cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys

I recommend you add the following sentence:
remove write permissions from group and other to your home directory and
.ssh directory.*