An HPC system is not like a regular computer that you can log into and begin using, there are multiple parts that make up the system. This page instructs users in using the applications that have the ability to use ssh. Ssh is one of the main methods for users to securely login to an HPC system. The Terminal, which is a native application on Linux and macOS, provides the means of using ssh.

Contents

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How to Login Using ssh

Step 1. The Terminal and ssh clients

Since Linux and macOS share a common ancestor in Unix they have a native application built right into the operating system and available on the desktop that provides the means of using ssh. This is called the terminal and is typically indicated by the icon below:

Open

While this is native to Unix-based operating systems, other options are available in ssh clients.

Step 2. Using ssh

In all of these methods, is important to know a few things about using ssh:

1. The host-name of the system

2. What your username is on the HPC System

3. Your password on the system

4. Anything else the system administrators require*, e.g. Two-factor authentication

• At The University of Wyoming, there are a few prerequisites that users need to have before they can log in to the local HPC system. Watch this video on the prerequisites or find them on the ARCC Prerequisites page.

Using ssh

In the Terminal the command for ssh is simple and can be executed by typing:

You send the command by hitting enter (or return) on your keyboard.

Enabling The Graphical Applications (Optional)

Sometimes a user will need to visualize data while working on an HPC system. This is done by enabling X11 forwarding. 

The X Window System (also known as X11, or just X) is a software package and network protocol that lets you interact locally, using your personal computer's display, mouse, and keyboard, with the graphical user interface (GUI) of an application running on a remote networked computer.

Using X forwarding in an ssh session on your personal computer allows you to securely run graphical applications (X clients) installed on HPC systems.

Enable Graphics ssh Command

In the Terminal all users need to do is use a flag to enable graphics with the ssh command

the -X (or -Y on Mac OS X) flag enables X11 forwarding. This does not default due to security reasons. 

FastX

FastX is the only X11 emulation solution that offers both a desktop client and a browser client. Create and display sessions running on remote Linux servers from any device with a modern browser. (Chrome, Firefox, Safari, Edge) You can display individual applications or full Linux desktops.

• Users do not need a Terminal or an ssh client if they use FastX in their favorite browser.

• At the University of Wyoming, users can use FastX to connect to our HPC System only if you are currently on the Campus domain or using the VPN. Users can also leverage FastX to provide them with a more robust remote graphics capability via an installable client for Windows, Mac, or Linux or through a web browser. Navigate to https://fastx.arcc.uwyo.edu and log in with your username, password, and second factor. There are also native clients for FastX for Windows, macOS, and Linux which can be downloaded from the StarNet website. 

For further information on FastX, visit the FastX page.

Teton ssh Access

Teton has login nodes for users to access the cluster. Login nodes are available publicly using the hostname teton.arcc.uwyo.edu or teton.uwyo.edu. SSH can be done natively on macOS or Linux based operating systems using the terminal and the ssh command. Although X11 forwarding is supported, and if you need graphical support, we recommend using FastX if at all possible. Additionally, you may want to configure your OpenSSH client to support connection multiplexing if you require multiple terminal sessions. For those instances where you have unreliable network connectivity, you may want to use either tmux or screen once you login to keep sessions alive during disconnects. This will allow you to later reconnect to these sessions.

Loren ssh Access

Loren has login nodes for users to access the cluster. Login nodes are available publicly using the hostname lorenlog1.arcc.uwyo.edu. SSH can be done natively on macOS or Linux based operating systems using the terminal and the ssh command. Although X11 forwarding is supported, and if you need graphical support, we recommend using FastX if at all possible. Additionally, you may want to configure your OpenSSH client to support connection multiplexing if you require multiple terminal sessions. For those instances where you have unreliable network connectivity, you may want to use either tmux or screen once you login to keep sessions alive during disconnects. This will allow you to later reconnect to these sessions.

Users also have direct access to some specialty nodes used for running GUI sessions

OpenSSH Configuration File (macOS)

By default, the OpenSSH user configuration file is $HOME/.ssh/config which can be edited to enhance workflow. Since Teton uses round-robin DNS to provide access to two login nodes and requires two-factor authentication, it can be advantageous to add SSH multiplexing to your local environment to make sure subsequent connections are made to the same login node. This also provides a way to shorten up the hostname and access methods for SCP/SFTP/Rsync capabilities. An example entry looks like where USERNAME would be replaced by your actual UWyo username: