Getting Connected - Teton

Owned by Abigail Smith (Unlicensed)
Last updated: Apr 22, 2021 by Dylan Perkins
6 min read

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. Older versions of Windows 10 do not have a native application that has the ability to use ssh, one must be downloaded. Those versions need a separate ssh client to be installed as an application. One of the commonly used applications is called PuTTY, but there are other options, such as MobaXTerm.

Contents

https://arccwiki.atlassian.net/wiki/spaces/DOCUMENTAT/pages/64192662

How to Login Using ssh

 ssh stands for 'Secure Shell'  This is one of the main methods for users to securely login to an HPC system.

For more information about Teton, specific examples with ssh the see ssh access section on this page.

Step 1. The Terminal and ssh clients

Linux/Mac

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:

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

Windows 10

Alternatively, older versions of Windows 10 does not have a native application that has the ability to use ssh. Those versions need a separate ssh client to be installed as an application. One of the most popular ones is called PuTTY, but there are other options, one of them being MobaXTerm, which provides a little more functionality. It is up to user preference on which one they like to use.

 

Newer versions of Windows 10 has a native application that can use ssh. In some cases, it is only available if you enable a setting, and in other cases, you can directly open the Windows command prompt and use ssh.

To make your options diverse, Windows 10 also provides a means of using Linux directly on the system. Windows Subsystem for Linux (WSL) is a compatibility layer for running Linux binary executables natively on Windows 10. 

For users who use Google Chromebooks, there are several ssh clients available to download through the Chrome Web Store. One of the most popular Terminal clients is an Android app called Terminus that can also be used on iOS. 

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

Using ssh

In the Terminal or Windows 10 Command Prompt or Windows subsystem for Linux, the command for ssh is pretty simple and can be executed by typing:

ssh username@host-name

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

When using an ssh client, like PuTTY,  a Windows 10 user may have to add their username and host-name in separate boxes, but the effect is the same.

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.

Linux/macOS

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

ssh -X username@host-name

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

Windows 10

On Windows, you need to also install a separate piece of software to enable X11. One of the most popular is called Xming, X Server for Windows. However, the ssh client MobaXTerm comes with X11 forwarding enabled by default and no additional software to install. 

ChromeOS

ChromeOS has an unusual Window System. There are workarounds for using X Server on ChromeOS, but none of them are recommended. 

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.

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.

ssh USERNAME@teton.arcc.uwyo.edu ssh -l USERNAME teton.arcc.uwyo.edu ssh -Y -l USERNAME teton.arcc.uwyo.edu # For secure forwarding of X11 displays ssh -X -l USERNAME teton.arcc.uwyo.edu # For forwarding of X11 displays

OpenSSH Configuration File (BSD,Linux,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:

WARNING: While ARCC allows ssh multiplexing, other research computing sites may not. Do not assume this will always work on systems not administered by ARCC.

Access from Microsoft Windows

ARCC currently recommends that users install MobaXterm to access the Teton cluster. It provides appropriate access to the system with SSH and SFTP capability, allowing X11 if required. The home version of MobaXterm should be sufficient. There is also PuTTY if a more minimal application is desired.

Additional options include, a Cygwin installation with SSH installed or the Windows Subsystem for Linux with an OpenSSH client installed on very recent versions of windows, enabling the OpenSSH client. Finally, a great alternative is to use our FastX capability.