Open OnDemand

Open OnDemand lets you work on the HTC cluster through a web browser — upload and download files, create and submit jobs, open a shell, and run GUI applications such as RStudio and Jupyter, without connecting over SSH. It was created by the Ohio Supercomputer Center (OSC), whose documentation (including video tutorials) is a good further reference.

Accessing Open OnDemand

Open OnDemand is reachable only from the University network. From off campus or on Pitt wireless, first connect to the GlobalProtect VPN (see Step 1). Then open https://ondemand.htc.crc.pitt.edu and sign in with your Pitt username (1) and password (2), then click Log in to Open OnDemand (3).

Open OnDemand login page with fields for Pitt username and password and a Log in to Open OnDemand button

Use a supported browser

Chrome and Firefox are fully supported. Safari and other browsers may work for some apps but are not officially supported.

The OnDemand Dashboard opens. The menu bar across the top is your starting point: Files for file management, Clusters for a shell, Jobs for composing and monitoring jobs, and Interactive Apps (along with the themed AI, Bioimage Apps, and Genomics Apps menus) for GUI applications. The Pinned Apps tiles below are quick-launch shortcuts to a featured subset; follow all available apps to see the rest. To end your session on the OnDemand portal, choose Log Out at the top right and close your browser.

Logging out of OnDemand does not terminate your Slurm jobs

An interactive job through OnDemand, such as Jupyter and RStudio, run as a Slurm job on a compute node. The Slurm job will run until the specified wall-time limit or until you click the red Delete button for the job shown under My Interactive Sessions. The good news is that if you lose internet connection, you can return to My Interactive Sessions later and reconnect to your job to continue where you left off or to monitor the progress.

Open OnDemand Dashboard showing the top menu bar and Pinned Apps such as Jupyter, RStudio Server, Code Server, MATLAB, and COMSOL

Managing files

The Files menu on the Dashboard lists your directories on the CRCD file systems — your home directory first, followed by your group storage under /ix, /ix1, and /vast. Selecting one opens the File Explorer in a new tab, with your home directory always shown in the left panel.

The File Explorer's toolbar lets you open a terminal, create files and directories, upload and download, copy or move, delete, navigate up a level, jump to an absolute path, copy the current path, toggle hidden files (dotfiles) and owner/permission columns, and filter by name. If a directory isn't listed in the Files menu, use Change Directory to reach it by its absolute path.

Shell access

The Clusters menu opens an in-browser terminal on the HTC login nodes — the same environment you would get by connecting with SSH.

Interactive apps

The Interactive Apps, AI, Bioimage Apps, and Genomics Apps menus — and the Pinned Apps shortcuts on the Dashboard — launch GUI applications such as Jupyter, RStudio, Code Server, MATLAB, COMSOL, and various domain tools, each on a compute node with dedicated resources. The pattern is the same for every app:

  1. Choose the app from the menu.
  2. Set the job parameters (version, cores, memory, time limit) and click Launch.
  3. Wait for the job to start, then click Connect to ….
  4. When finished, return to the Dashboard and click the red Delete button to end the session and free the resources.

Deleting your Interactive Session when done is not optional

Closing the app's browser tab does not end the job. Until you click Delete on the Dashboard, the interactive session keeps consuming your allocation.

‘Failed to connect’ right after launching

If you click Connect and see Failed to connect to htc-n**.crc.pitt.edu:<port>, the app's web server usually isn't ready yet. Wait a minute or two and refresh.

For the per-app details — Jupyter (and Python/conda environments), Jupyter on GPU, RStudio, MATLAB, and the genomics apps — see OnDemand Interactive Apps.

FAQ

I can't log in — I get an "Internal Server Error" mentioning no space left on the device. OnDemand writes files to your home directory at startup, and your home has a 75 GB quota. If it's full, connect to a login node (or use a file-transfer tool) and remove or relocate files to your group storage (/ix, /ix1, /vast).

My session closes shortly after starting, showing "Completed" with only a message that the card will be retained for a few more days. Open the link after Session ID: and read output.log in that folder — it usually explains the error. If it's unclear, submit a help ticket with the log contents or the session ID.