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Accessing the Cluster

Connection to the Cluster

REMINDER: If you want to access the clusters from outside Wistar's network, you must use the Wistar VPN.

SSH Login

Login with to the cluster at WI-HPC once connected to the Wistar Network. If necessary, you can connect via the fully qualified domain name wi-hpc.wistar.upenn.edu (note this will be changing to wi-hpc.apps.wistar.org)

Using a terminal, connect to the cluster

ssh username@wi-hpc.wistar.upenn.edu

First Login - Testing Directory Access

When first connecting to the the WI-HPC cluster, you should check to make sure that you have access to the appropriate directories. Directories are Auto-mapped when accessed - so they may not be seen with an ls -al command until after you attempt to access it.

Key Directories include:

  • /applications
  • /wistar/labsharename
  • /home/username
  • /resources/datasetsharename (coming soon)

Troubleshooting

Login Checklist

If you are having trouble logging into a cluster, please use the checklist below to check for common issues:

  • Make sure you have submitted an HelpDesk Ticket and have gotten word that we created your account for the cluster.
  • Make sure that the cluster is online in the System Status (pending) page.
  • Check the hostname/IP address for the cluster.
  • Make sure your computer is either on Wistar's campus network (ethernet or Wistar-Wifi-Internal wireless) or Wistar's VPN.
  • If you get an error like could not resolve hostname you may have lost connection to the Wistar network. If you are sure you have not, make sure that you are also using the Wistar's DNS servers (172.16.2.220,10.60.0.3).
  • Your home directory should only be writable by you. If you recently modified the permissions to your home directory and can't log in, please send an email to the IT Helpdesk at helpdesk@wistar.org and we can fix the permissions for you.

If none of the above solve your issue, please send an email to the IT Helpdesk at helpdesk@wistar.org with your username and information on how you were attempting to access the cluster.

Common SSH Errors

REMOTE HOST IDENTIFICATION HAS CHANGED

If you are seeing the following error:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
....
Offending key in /home/user/.ssh/known_hosts:34
...

This usually means that the keys that identify the cluster login nodes have changed. This can be the result of system upgrades on the cluster. It could also mean someone is trying to intercept your ssh session. Please by sending a email to the IT Helpdesk at helpdesk@wistar.org if you receive this error.

If the host keys have indeed changed on the server you are connecting to, you can edit ~/.ssh/known_hosts and remove the offending line. In the example above, you would need to delete line 34 in ~/.ssh/known_hosts before you re-connect.