Accessing Linux Environments

Overview

Many of the academic Linux-based servers hosted by the Information Services Data Center have some commonalities to provide consistency for faculty and students in accessing and utilizing the resources.  This article is meant to provide some reference material for the most common procedures but please note that they might not all be applicable to all such servers.  If you are working with an academic server hosted in the Data Center that does not follow these instructions, students should contact their instructor or research advisor for the appropriate information.  

Details

Access 

Please note that if you are connecting from off-campus to any of the aforementioned servers and workstations, you must first connect to UR VPN to act as a conduit for your SSH client.

SSH (Secure Shell)

SSH is the most common method for communicating with academic Linux servers.  It is primarily a text-based communication method and is secure due to an underlying encryption protocol.

SSH Sessions From Windows Computers

Software commonly available on University Windows computers for communicating via SSH include PuTTY and Windows PowerShell.  PowerShell is installed on Windows by default and one can download PuTTY from https://www.putty.org . To use PuTTY, follow these steps:

1.    Open PuTTY.
2.    Enter the destination name for the Host Name (ex. servername.richmond.edu ).
3.    Leave the other fields with the defaults (Port: 22, Connection type: SSH).
4.    Click the Open button.
5.    You may get a security alert asking if you trust the server’s SSH fingerprint.  Click the Yes button.
6.    Enter your NetID for "login as:" and then enter your NetID's password.
7.    If you wish to simplify this process in the future (assuming you are using your own computer, you can create an SSH key that will automate that process.  Please refer to instructions available at https://www.ssh.com/academy/ssh/putty/windows/puttygen .

SSH Sessions From Macintosh Computers

Software commonly available on University MacOS computers for communicating via SSH include Terminal and XQuartz.  Terminal is installed by default on Macs while XQuartz can be downloaded from https://www.xquartz.org/ .  To use Terminal, follow these steps:
1.    Open the Terminal application found under Applications >> Utilities or via the Spotlight search tool.
2.    Type 'ssh netid@servername.richmond.edu' without quotes and substituting your NetID and chosen server at the terminal prompt and hit Enter.
3.    Enter your NetID's password and hit Enter.  You may get a security alert asking if you trust the server’s SSH fingerprint, type Y and hit Enter.
4.    Enter your NetID for "login as:" and then enter your NetID's password.
5.    If you wish to simplify this process in the future and you are using your own Mac, you can create an SSH key that will automate that process.  Please refer to instructions available at https://sl.richmond.edu/T .

Remote GUI Session Using X11 Forwarding

It is often desirable to access the graphical user interface (GUI) of an application or the entire desktop session.  In fact, some applications are only operable through a GUI.  Although there are newer technologies available, the common tool on Linux systems use X11 Forwarding, i.e., the graphical session is forwarded via X11 from the remote computer to the XServer application running on your laptop so you can see it.  The technology requires opening the graphical application on the remote Linux system as well as an X server application on your computer that can display the X session that is being forwarded from the server to yours.  
Please note that some University Linux systems do not have a GUI desktop environment installed so you may only be able to use the individual X window applications.
•    For individual X applications like Emacs, Firefox, Matlab, and RStudio, you will first need to connect to the server using X11 Forwarding (see details below) and when you run the X application, your application window should open in the X11 app on your computer remotely.
•    If the remote Linux system has a GUI desktop installed such as Gnome or KDE, you may be able to access the entire GUI desktop remotely.  For some servers, the command to run may be 'startx' .  In the case of Mathematics and Computer Science Department, there is a script one can run called xwinrhel7.sh that is installed on the mathcs workstations and turing2 server.  It will load a Gnome desktop session for the current user.

Remote GUI Sessions on Windows Computers

There are a multitude of available X server applications if you are using a Windows computer to access the University Linux systems.  A few of the common examples include Cygwin, XMing, and MobaXterm.  MobaXterm is one of the best applications to use for X sessions since it includes both an SSH client for initiating the connection and the X server technology on your computer.  It is a commercial application with a free version for personal use.  Instructions for installing and using MobaXterm are available at https://mobaxterm.mobatek.net/ .  However, some basic instructions are included here.  

1. Open MobaXterm.
2. If you see a terminal session in the main window with a prompt that includes the time and your username and machine name of your computer, you can skip to step #4.
3. Select Terminal from Main Menu and then Open a new tab .  A terminal session should open.
4. Type 'ssh -X netid@servername.richmond.edu' without quotes and substituting your NetID and chosen server at the terminal prompt and hit Enter.
5. Enter your NetID's password and hit Enter.  You may get a security alert asking if you trust the server’s SSH fingerprint, type Y or Yes and hit Enter.
6. Enter your NetID for "login as:" and then enter your NetID's password.  MobaXterm may offer to store your password which will make future SSH sessions easier without needing to enter your password each time.  However, you can also follow MobaXterm's web-based instructions to create SSH keys to automate the process without having to store your password.
7. Once connected, you can use your SSH session like usual, but you may also launch an X application from that terminal session.  When starting an app such as Firefox, the X application on your computer should open with the Firefox window from the server.
8. When finished with your remote session, it is a best practice to log out of your account from inside the Linux environment X window so that it gracefully exits the session. 
9. In the original terminal session, you should see that the GUI session has been killed.  You can then type ‘exit’ to end the SSH session as usual.

Remote GUI Sessions on MacOS Computers

There is one option on Macs to use X windows.  XQuartz needs to be installed on your computer, and it can be downloaded and installed from https://www.xquartz.org/ .  Once installed, follow these steps:

1. Start XQuartz (if it is not in the dock, you can search Spotlight (Command-space) to find it).
2. Once opened, click the Applications menu and then Terminal to open a new terminal window (or use the Command-N key combination).
3. In the new terminal window, type ‘ssh -X netid@servername.richmond.edu’ without the quotes and substituting in your NetID and your chosen server and then hit the Enter key.
4. Once connected, you can use your SSH session like usual but you may also launch an X application.
5. When finished with your remote session, it is a best practice to log out of your account from inside the Linux environment X windows so that it gracefully exits the session. 
6. In the original Terminal session, you should see that the GUI session has been killed.  You can then type ‘exit’ to end the SSH session as usual.

See Also

Academic Services and HPC Clusters (list)

VPN