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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

Pawsey supercomputers are accessed remotely through the SSH protocol. Most of the time users employ the ssh command-line tool installed on their computers, which allows executing commands through a terminal window; other programs implementing the SSH protocol may be used. Within many supercomputers, the nodes on which jobs are run, often referred to as "compute" nodes, will NOT be directly accessible 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 (like some profilers) you can use X forwarding over SSH.

When a connection is established with any of our systems, it is to a login node. Login nodes are the "front desk" of the system, and they allow users to manage their workflows, edit files, and submit jobs to the scheduler to be executed on the compute nodes. The compute nodes are where the main computations are processed and they can be accessed through the different queues or partitions managed by the scheduler. These concepts are illustrated in figure 1.

Use SSH to connect to a supercomputer

The login node of a Pawsey supercomputer is reachable through the Internet at an assigned public hostname. The hostname of the login nodes of each Pawsey's supercomputer is listed in table 1. The linux command ssh should be used by users to connect to the login node of a remote host, as shown in the following line.

$ ssh [options] <username>@<hostname>

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

Generic names for connecting to Pawsey Supercomputers

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' hostnames.

$ ssh username@setonix.pawsey.org.au
Password:
Last login: Mon Jan 10 11:07:13 2022 from 130.116.145.55
##############################################################################
#                    Pawsey Supercomputing Centre                            #
#        Empowering cutting-edge research for Australia's future             #
#                                                                            #
#     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 using Pawsey facilities you agree to the Conditions of use available at
 https://support.pawsey.org.au/documentation/display/US/Conditions+of+Use
 
===============================================================================
username@setonix-1:~> hostname
setonix-1

Related pages

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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.

Login nodes

The hostname of a supercomputing system is often a pseudonym of several login nodes that the system may have. When connecting remotely, connections are randomly placed on a login node from where you interact with the rest of the system using a round-robin DNS technique. The actual hostname of the login node ("setonix-1" in the example below) can be easily obtained by executing the hostname Linux command after an SSH connection has been established. Terminal 1 illustrates an SSH connection to a login node and outputting the hostname.

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

Connection methods

Several connection methods are listed below. The standard recommendation is the use of the SSH-client from a terminal together with an SSH-key for authentication.