This section explains how to connect to and interact with Pawsey supercomputing systems.

Prerequisites

To access a supercomputer, users have a Pawsey account, comprising a username and a password. The account must also be a member of an active project allocation on the selected supercomputer. For new users, an account creation email with instructions is sent when you receive an allocation or are added to a project.

Introduction

Figure 1 illustrates some components of a supercomputer

Use SSH to connect to a supercomputer

As detailed above, within many supercomputers, the nodes on which user jobs are run, often referred to as "compute" nodes, will NOT be directly accessiible from the outside world.

In order to be able to request that jobs be scheduled onto the "compute" nodes, and/or to move data around ahead or, after, running computational tasks, many supercomputers will have "front-end" nodes into which users can login, and then perform non-computational and administrative tasks.

Logging in to such "front-end" nodes at Pawsey requires users to run an SSH (Secure Shell) client on their local machine.

To execute programs that display a graphical interface you can use X forwarding over SSH.

Pawsey currently has two classes of "front-end" nodes, one group, usually referred to as "login" nodes, which are designed for the submitting of jobs and editimg of files, and a second group, usually referred to as "data-mover" nodes, which have higher-speed connectivity to various Pawsey storage systems than the "login" nodes, and which are thus recommended as the group of nodes from which to perform any data transfer operations, both within Pawsey, and when moving data into, or out of, Pawsey.

In order to try and ensure that "front-end" node responsiveness isn't slowed down by having too many of our users on one "login" or "data-mover" node at the same time, Pawsey, in common with many other supercomputing centres, operates a system whereby users are encouraged to connect to a generic name for the service, "login" or "data-mover", which allows for a mechanism, known as "DNS round-robin", to transparently redirect the user's connection to one of a group of nodes, and so balance the load across the group.

At Pawsey, users will typically connect to the "front-end" nodes using the generic names shown in Table 1, but will end up being logged into nodes which have specfic hostnames

Table 1. List of Pawsey's supercomputing systems

where NN will be a zero-padded two-digit number

Using a command-line SSH client

When connecting using a command-line SSH client, the format of the command will be

ssh [options] <username>@<generic-hostname>

Replace <username> with the username of your Pawsey account, and <generic-hostname> with one of the hostnames listed in Table 1.

To authenticate the connection, a user can either enter the password for each connection or use an SSH key. SSH keys provide more security and eliminate the need to enter the password each time the ssh command is executed.

An SSH key is an access credential in the SSH protocol. Its function is similar to that of username and password but enables automated processes and single sign-on users.

Example of logging into a Pawsey system

Should a user need to report an issue to Pawsey's Help Desk, the Help Desk will want to be supplied with the specfic hostname into which the user had logged in.

Once logged in to one of a group of nodes, the specific name of the node can be seen in the default shell prompt, although, should the user change their prompt, the actual name of the node can always be obtained by running the 'hostname' command.

Terminal 1 shows an example of a user logging in to one of Setonix's "login" nodes, where the specific name of the node can be seen in the default prompt, as well as the running of the 'hostname' command

Note that the complete "MotD" (Message of the Day) content has been truncated in the example output

mymachine$ ssh username@setonix.pawsey.org.au
Password:
################################################################################
# 
# NOTICE TO USERS 
# 
# .
# .
################################################################################
Last login: Mon Jan 10 11:07:13 2022 from 130.116.145.55
                  Pawsey Supercomputing Research Centre
               Enabling Science and Accelerating Discovery

This service is for authorised clients only. It is a criminal offence to:
- Obtain access to data without permission
- Damage, delete, alter or insert data without permission

By continuing to use this system, you are agreeing to the terms and conditions
at https://pawsey.atlassian.net/wiki/display/US/Conditions+of+Use
.
.
Support and helpdesk is staffed Monday - Friday 09:00 to 17:00 AWST, and can be
contacted via email (help@pawsey.org.au) or web (https://pawsey.org.au/support/)

  Please include your username, project name, relevant Job IDs,
  and paths to batch scripts and any output/error logs with your query.
  If your query relates to connectivity, please include the IP address
  of the machine you are connecting from.
.
.
----------------------------------------------------------------------------
username@setonix-03:~> pwd
/home/username
username@setonix-03:~> hostname
setonix-03

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