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High Performance & Scientific Computing

Access and Login on ISAAC-NG


The focus of this document is accessing the ISAAC-NG from various terminal programs using ssh (Secure Shell). To get access to the ISAAC-NG through OpenOnDemand in a web browser, please refer to the OpenOnDemand document. This document assumes you currently possess a valid user account and have familiarity with remote access methods.

Here are the login hostnames:

Login NodeHostname for SSH

Mistakes to Avoid on ISAAC #1: Avoid running computational jobs on the login nodes
The login nodes on ISAAC are shared by all users and should not be used to run computational tasks. They can be used for job preparation such as lightweight file editing, code compilation short tests, software installation, job submission and monitoring. However, any intensive computation on the login nodes would affect other users not being able to use a cluster login node or, in the worst case scenario that has happened, could render the login node inoperable.


A Secure Shell client is needed in order to connect to ISAAC-NG through SSH. In MacOS and most Linux distributions, a ssh client is built-in to the operating system. On Windows, PuTTY and MobaXterm can be used to provide ssh capability. Review the documentation on those clients to learn about their usage. Recent updates to Windows 10 have added built-in support for ssh. If it is not installed on your version of Windows, please refer to Microsoft’s documentation on OpenSSH. It can then be accessed with the Command Prompt or Windows PowerShell in the same way you would access ssh from a terminal within MacOS or Linux.


In addition to a ssh client, you will need the Duo app on your mobile device. The app can be downloaded from the Apple App Store for iOS users or from Google Play for Android users. New users should be automatically enrolled in Duo; existing users, however, must associate their UT NetID with their NICS account. To do this, navigate to the NICS user portal and click the link to associate your UT NetID with your NICS account. If you skipped Duo enrollment when you created your NICS account, then you must also associate your UT NetID with your account. For more information on Duo, visit their website.


For MacOS and Linux Users

To begin, open a terminal. At the prompt, type ssh <your-NetID> When prompted, supply your NetID password. Next, type 1 and press Enter (Return). A Duo Push will be sent to your mobile device. You may use the 2 options to receive a SMS message on your mobile device with a code that you should provide at the prompt. Regardless of the Duo option you choose, you will be logged into the ISAAC-NG once you successfully authenticate.

For Windows Users

On Windows, the process for connecting to the Open Enclave depends on the client you use. If you run an updated Windows 10 machine, you may use PowerShell or Command Prompt to access ssh. Either terminal will work for connecting to the Open Enclave. Once you open either PowerShell or Command Prompt, follow the same steps MacOS and Linux users use to connect to the Open Enclave.

For older Windows systems, such as Windows 7 or 8, you should use PuTTY to connect to the Open Enclave. Launch PuTTY. Make sure the “Session” menu is selected in the left pane. In the right pane, type in the “Host Name (or IP address)” box. Verify that the port is set to 22 and that ssh is set as the connection type, then select “Open.” You will be prompted to provide your NetID, followed by your NetID password. Next, you will authenticate with Duo. The Duo options remain the same as they do for MacOS and Linux. Once you successfully authenticate, you will be logged into the ISAAC-NG.


For MacOS and Linux Users

Open Enclave resources support X11 forwarding, which enables the use of graphical tools. On most Linux distributions, X11 is built-in to the operating system. On MacOS, the XQuartz system handles X11. You can access XQuartz by typing xterm in a standard Terminal.

Open your X11 terminal of choice, then execute ssh -X <your-NetID> to connect to ISAAC-NG with X11 forwarding enabled. If the connection does not work, replace -X with -Y. Because the option is case-sensitive, make sure you use capital letters. Upon connecting to the Open Enclave, type xeyes or clock to verify that the X11 system is functional. If neither of those programs work, review the documentation for the client you chose and check your X11 terminal configuration.

For Windows Users

Windows does not have a built-in X server to use for X11 forwarding; therefore, a third party X server must be installed to enable its use. If you require X11 forwarding on a Windows machine, it is best to use PuTTY as your ssh client and xming as the X server. Download and install both applications. Once they are installed, start xming, then open PuTTY. In the left pane, expand the “Connection” menu. Under the “SSH” menu, select “X11.” Check the box that says “Enable X11 forwarding.” Be aware that this will only apply to your current session unless you save it for future use. If you do not save the session, you must manually enable X11 forwarding each time you require it. With X11 enabled, use PuTTY to connect to the Open Enclave as you normally would. You may test X11 with the xeyes and xclock commands.