# Interactive HPC

Interactive sessions provide real-time access to compute resources. Interactive sessions can be used to prototype workflows, compile code, and analyze or visualize data. When prototypes are ready to run at scale on MSI HPC systems, use interactive sessions to connect and submit batch jobs on the HPC resources.

**Note:** To access MSI systems you will need to be either located on a UMN campus and connected to the `eduroam` network, or connected to the UMN VPN from an off-campus location.

## Types of Interactive HPC

### Interactive Session Using the Command Line

Once connected to MSI's HPC cluster via SSH, you can start an interactive session in the command-line interface with `srun`:

```bash
srun -N 1 -n 1 -t 4:00:00 -p interactive --tmp 20gb --pty bash
```

This example connects a user interactively to one core of one HPC node, with a time limit of 4 hours, using a Bash shell. You can then use the command line to run software interactively.

### Open OnDemand

[Open OnDemand](https://ondemand.msi.umn.edu/) provides interactive access to MSI's compute cluster through your web browser. With Open OnDemand you can access your files stored on MSI systems, view your current jobs on the MSI clusters, use a command-line interface in your browser, or start an interactive desktop session with configurable memory and compute resources. OnDemand also lets you launch graphical user interfaces for commonly used applications such as Jupyter Notebooks, RStudio, Abaqus, COMSOL Multiphysics, and MATLAB.

Most users feel more comfortable interacting with GUIs over shell prompts. Interactive desktops via Open OnDemand give users the look and feel of a personal Linux laptop or workstation, but also include all tools, modules, and data one would access via the command line.

See [Open OnDemand Support](https://msi.umn.edu/getting-started/help/knowledge-base/open-ondemand-support).

### Citrix

Certain MSI applications are not compatible with the Linux-based operating system used on the HPC cluster, and need to be run in a Windows environment instead. Citrix connects a user to a graphical Windows environment where they can access these specialized Windows applications for modeling and data analysis. See [Connect to a Citrix Windows Virtual Machine](https://msi.umn.edu/getting-started/getting-started-and-access/interactive-connections-faqs/how-do-i-connect-citrix-windows-virtual-machine).