Connect to the campus VPN and log into the JupyterHub URL for your course. Ensure the URL is prefaced with 'https://'.
Select 'Admin' at the top
Select 'stop server' for select users, or 'Stop All' at the top to end all sessions. Note the 'Last Activity' and 'Running' columns to identify idle sessions.
Course staff must regularly log in and close sessions to prevent the JupyterHub server from freezing
If you cannot access the JupyterHub interface, you can still access the virtual machine hosting your course's JupyterHub instance via ssh and reboot the server.
ssh <NETID>@<HOSTNAME># The hostname of your server follows the URL for your JupyterHub instance i.e.: https://phys999-jupyter.engrit.illinois.edu implies a hostname of phys999-jupyter.engrit.illinois.edu
Once you are logged into the system, you can just run "sudo reboot" and the machine will reboot.
Please note, the jupyterhub service on the server may take up to 15 minutes to start after a reboot.