Logos: Shared Linux Server

A Typical Rack-Mounted Server. This one isn't ours.

The Mathematics, Computer Science, and Statistics programs together maintain a powerful, centralized Linux server named logos that is accessible from on or off campus. For most computer science courses, all of your files, code, programs, and data will be stored on logos. Other courses will have you running software on logos to get better performance or take advantage of the software we already have installed.

Having Trouble?

If you are having trouble accessing logos remotely, please see below.

What happened to radius?

Our previous department compute server, named radius, has been retired. All data and accounts have been transfered from radius to logos.

In the Lab or Nearby (using the NUCs)

When in the Integrated Science Complex or nearby, you can take advantage of the system of networked terminals (called "NUCs") in Swords 219, Haberlin 136, and the McBrien Student Lounge (Swords 3rd floor), all of which are configured to be able to easily and transparently access logos and all of the software and files you have stored there. All of these NUC terminals work equally well for accesing logos.

Outside the Lab

You can also access logos from your own computer, using a variety of remote-access software, described below. All of this software is industry-standard and very widely used—for cloud computing, software development, scientific research, business and e-commerce, etc.— so learning how to use it effectively will almost certainly be worth it regardless of what you plan to do after Holy Cross.

There are a few different categories of remote access. You'll probably use a combination of all them at various times:

• Software for editing and accessing remote files.
• Using a text-only command-line remote shell to run commands.
• Transferring files between logos and your own computer.
• Software to edit plain-text files locally on your own computer.
• Full graphical and desktop access with support for graphical software.

All the software we recommend on this page is free, except where noted. You should not have to pay to access logos.

Logos only allows direct remote access from certain secure, authenticated networks, such as on-campus "HCWireless" WiFi, wired on-campus dorm networks, and the computer labs. Other, insecure and off-campus networks require installing and activating the Holy Cross VPN.

• ✅ If you have a laptop and are connected to the on-campus "HCWireless" WiFi network, you can access logos remotely without the VPN.
• ✅ If you have a desktop or laptop with a wired on-campus connection, you can access logos remotely without the VPN.
• ❌ If you use the "HCGuest" WiFi network, you must use the VPN to access logos.
• ❌ If you are off campus or using a cell-phone hotspot, you must use the VPN to access logos.

We recommend you install Visual Studio Code (also known as "VS Code" or "vscode") on your own computer. This is a fairly popular "modern" code editor, with syntax coloring, and other helpful features. It fulfills almost all of the needs identified above: it has support for editing and accessing remote files; it provides a text-only command-line remote shell; it can easily transfer files to or from remote servers; and it can edit plain-text files locally on your laptop. The only thing it can't do is graphical access. For CSCI 131, vscode alone is enough for the first few labs and several of the projects, with no other software needed. For CSCI 132, vscode is enough for everything.

How to install and configure vscode to work "seamlessly" with our logos server:

1. Download, install, and run Visual Studio Code WARNING: Please be sure to use a current edition (1.81 or later). If you previously installed some older version, please update. Earlier versions will cause significant issues for our servers.

2. Go to "extensions" (boxy icon in the vscode window left margin, or Control-Shift-X), search for the "SSH" extension, and install it. There will be many similar extensions available: get the one named "Remote - SSH" (tag: "ms-vscode-remote.remote-ssh") published by Microsoft with over a million downloads. (If you have a very old and un-updated version of Windows 10 without the "OpenSSH" components, follow the "Installing OpenSSH" steps here. If using an even older version of Windows, before Windows 10, you will probably need to install git which comes with the necessary ssh client software.)

3. If you are using the HCGuest WiFi or are located off campus, you'll need to activate the Holy Cross VPN before completing this next step. Once the "Remote - SSH" extension is installed, click the small green icon in the vscode window bottom left corner, select "Remote - SSH: Connect to Host...", and enter username@logos.holycross.edu as the host. Replace "username" with your Holy Cross login name, e.g. aturing22. Use the same password you would use for Moodle, STAR, and Canvas. You might need to enter the password twice. If asked to select the "Remote Platform", pick Linux. All of these settings can be saved in vscode.

Once connected, you can browse folders on logos (click the file icon on the left side), open and edit files on logos (just click a file in the left panel), open a terminal window with a text-only command-line remote shell (under the menus, "Terminal > New Terminal..."), transfer files to or from logos (just drag-and-drop files using the vscode side panel and your own computer's desktop), all you can do all this staying within vscode.

Check your vscode connection to logos: After connecting, you should probably have two vscode windows. One is still working on your local machine. The other, new window, is connected to logos and should show a green box in the lower left corner with a note similar to "SSH: logos.holycross.edu". Here is a screenshot demonstrating a successful connection using vscode.

Try out the file browser and vscode terminal: While connected to logos, select "Terminal > New Terminal..." from the menus. You should get a split-screen window with a terminal in the bottom half of the screen, saying something like aturing22@logos~$. If you type things in that lower window, it should respond. If you type whoami, it should print your login name, for example. While still connected to logos, also try clicking the file-open icon in the left side panel (if asked, next click "Open Folder" then, when prompted for the folder name just say "OK" to the default, which should be something like "/home/stu/cl2022/aturing22"). This should show a list of all your logos folders and files in the left panel. You might not have many files or folders yet. Here is a screenshot demonstrating both a vscode a terminal and the vscode file browser while connected to logos.

Note: vscode does not support graphical applications in its built-in terminal—the vscode terminal is entirely text-only mode. So for projects that need graphical support, you'll have to run them outside of vscode, using the graphical software described below.

If the above instructions aren't enough, or you'd like step-by-step pictures, you can follow this very extensive tutorial and instructions for using vscode with the SSH extension. Or, try the official vscode ssh tutorial, which also detailed information about using the SSH extension (ignore the tutorial parts about Azure Cloud Computing, and substitute logos.holycross.edu instead).

Also Recommended: SSH for Text-Only Remote Shell Access

SSH, the secure shell protocol, is the standard way to access remote linux servers. It is used extensively in industry and research, and even for things like hacking at home, cloud computing, or scientific computing. So it's worth learning. To use SSH from your laptop, you need an SSH "client". Fortunately, Windows 10 and Mac OS both come with SSH clients already installed, so there is no more software needed. All you have to do is learn to use it.

Check your SSH connection to logos: After connecting, you should see a friendly greeting in your terminal window, with a prompt like "aturing22@logos~$". If you now type commands in the terminal window, it should respond. For example, if you type whoami, it should print your login name. Here is a screenshot demonstrating a successful connection using SSH.

The biggest drawback to using SSH is that it is entirely text-only mode. By itself, SSH does not support graphical applications. Typically, if you launch an editor (like emacs, gedit, or vim) within an ssh terminal window, you will not be able to use your mouse to point and click, and will instead need to rely purely on keyboard shortcuts for editing. Of course, the advantage is that using keyboard commands is much faster than using the mouse, even if it takes some time to become proficient. But for projects that need graphical support, you'll have to use the graphical software described below.

Another thing you should note: once you have your terminal window logged into logos, when you start certain programs (like emacs), they will run right inside your terminal window. And they will completely take over the terminal window until you quit, so you won't be able to enter any Linux commands until then. Once you quit emacs or whichever program has taken over your terminal, it goes right back to being a regular terminal again. For this reason, it is common to just open two or three separate SSH windows, so you can have one for your editing, one for your Linux commands, and other terminal windows for other things.

Transferring Files Between Your Laptop and logos

Sometimes you might want to copy files from your laptop to logos, or vice versa. For example, if you find that editing files remotely is slow, or you know you won't have good internet access, you might rather copy all your files from logos to your laptop and edit them locally, then later copy them back to logos when you are finished. You'll need two things.

First, you need a way to transfer files. SCP lets you copy files back and forth between your logos home directory and your laptop. There are command-line versions of scp, which must be used from within the terminal, and also several frinedly "graphical SCP" programs you can install. Next, once you are able to transfer files, see below for instructions on how to edit plain-text files locally on your laptop.

If you are transfering files back and forth between logos and your own laptop, you probably need a way to edit the files locally on your laptop. There are plenty of plain text editors to choose from, and many have built-in support for highlighting and indenting code.

Big Warning: Java, C++, and nearly all other programming languages use plain text files, and you must edit them with a plain text editor. Relying on "word processing" programs like Microsoft Word, Google Docs, or other "rich text" programs often leads to trouble. Google Docs, for example, has an option for downlading as "plain text" but the file it produces is not actually truly "plain text" and probably won't work with Java or C++. We recommend using an editor designed for programming, or at least an editor made specifically for plain-text editing.

The X11 Protocol, in combination with SSH, is a traditional way to get graphical remote access to a Linux machine. Confusingly, what you need on your laptop is the X11 "server" software. The X11 "client" software runs remotely, and is already installed on logos. You may or may not get a full "desktop" experience, depending on X11 server software you use. But when you run graphical programs (like emacs in GUI mode, web browsers, or projects that use graphics), they should open in their own window as if they were running locally on your laptop, and you should be able to use the mouse to interact with the remote programs.

Warning: Using X11 can be slow (and sometimes extremely slow), especially if you are connecting from off campus or if you have a less-than-stellar internet connection.

Check your X11 connection to logos: After connecting with X11 enabled, you should be able to run the xeyes command in a terminal window. It may take a moment, but some eyes should pop up in a new window. You can close the window or press Control-C in the terminal to halt xeyes. (This program is old and mostly useless, but is a traditional way to check if an x11 connection is working.) If it instead says "Error: Can't open display", then something has gone wrong. If using ssh with XQuartz on Mac, maybe you forgot the "-Y" after the ssh command, or forgot to run XQuartz before running ssh. If using MobaXTerm on Windows, be sure to run the xeyes command within MobaXTerm, not in a separate ssh terminal outside MobaXTerm.

Troubleshooting remote access to logos

Some steps to take if you are having trouble accessing logos remotely:

1. Ensure you are on HCWireless and are NOT using the the VPN. Or, use the VPN with HCGuest or some other untrusted network besides HCWireless. In other words, trusted network, or the VPN, one or the other but not both.
2. Ensure you are typing your login all lowercase, e.g. "aturing25@logos.holycross.edu", not "ATURING25", and not "ATuring25", etc.
3. Ensure you are using the same password you normally use for STAR.
4. If using VSCode, make sure you are using a recent version. Some students report that deleting VSCode from your computer then re-installing it helps.
5. When using VSCode to connect, if it asks whether the system is "Linux" or "Windows", be sure to pick "Linux", since logos is a Linux server.
6. Open Terminal.app (on MacOS) or cmd.exe (on Windows), and type "ssh yourlogin@logos.holycross.edu". If it asks for a password, type it (even if you don't see anything happen as you type, go ahead and type the password anyway). This can help narrow down if the problem is the network (if it doesn't even ask for a password), or your account (if it asks for a password but doesn't go beyond that), or VSCode (if you can log in using Terminal.app / cmd.exe, but not using VSCode).
7. If none of the above work, send email to the ITS Helpdesk and the Math/CS server admin. Please mention the results of the steps above and any specific error messages you might be getting. If possible, please also include your IPv4 address from your settings (for MacOS, look in Network Settings > WiFi > Details > IP Address; For Windows, try Settings > Network & Internet > Wi-Fi > Properties > IPv4 Address). Websites that claim to tell you your website won't work propertly for this step, you must go into your settings instead.