Using Passwordless SSH

08-May-2008

Introduction

Passwordless SSH is required on the Shared Computing Resources if you need to run MPI jobs using mpirun. The mpirun command spawns copies of your executable on all of the nodes allocated to you by PBS. It will communicate with these nodes via SSH so it is necessary that SSH is configured with SSH host keys (passwordless SSH) for your account. This document describes how to enable passwordless SSH on these systems.

Create Host Key

The first step in establishing passwordless SSH is to create your host keys. Login and run the ssh-keygen command. Accept all of the default values and do not enter a passphrase.


username@hostname:~> ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/users/username/.ssh/id_rsa):
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /users/username/.ssh/id_rsa.
Your public key has been saved in /users/username/.ssh/id_rsa.pub.

Add Host Key to authorized_keys File

After you have created your host key above, append the contents of /users/username/.ssh/id_rsa.pub to /users/username/.ssh/authorized_keys. This will enable mpirun to login to the compute nodes using SSH without a password.