Setting up Passwordless SSH

SSH is often used to login from one system to another without requiring passwords. This will be required when you run a cluster, it will not ask you for the password again and again.

 steps:

1. First log in on Host1 with user user1 and generate a pair of authentication keys. 

    Do not enter a passphrase:

    user1@Host1:~> ssh-keygen –t rsa

          2. Now use ssh to create a directory ~/.ssh as user user2 on Host2 .

                ( if directory already exists, then no issues with that)

     user1@Host1:~>ssh user2@Host2 mkdir –p .ssh

     user2@Host2’s password:

3. Finally append Host1's new public key to user2@Host2:.ssh/authorized_keys and 

     enter Host2's password one last time:

     user1@Host1:~>cat /home/hadoop/.ssh/id_rsa.pub | ssh user2@Host2 'cat >>         .ssh/authorized_keys'

    hadoop@Host2’s password:

    now you can login to Host2 using user2 from Host1 machine

    user1@Host1:~>ssh user2@Host2 hostname

   NOTE: If you face any issue while logging in, please make the below changes:

•    Put the public key in .ssh/authorized_keys2
•     Change the permissions of .ssh to 700
•      Change the permissions of .ssh/authorized_keys2 to 640