Passwordless ssh

It is very convenient to use ssh to login into different workstations or for instance our Beowulf cluster elegast without having to re-type your password all the time. It is possible to setup things in such a way that this is possible. Here's the howto.

First you need to generate a so-called RSA key. Type

ssh-keygen -t rsa

This will create two files: id_rsa and id_rsa.pub. The first should be kept secret, the second is public. You should now login into the remote machine. If the file ~/.ssh/authorized_keys exists, append the contents from the file id_rsa.pub to it. If it does not exist, create the directory ~/.ssh (with permissions rwx for yourself and no permissions for group and others) and the file authorized_keys (with permissions rw- for yourself and r-- for group and others) with as its contents the file id_rsa.pub.

You should now be able to do passwordless ssh logins.