HPC FAQ - Logging in
Supercomputer documentation is always a work in progress! Please email questions, corrections, or suggestions to the HPC support team at firstname.lastname@example.org as usual. Thanks!
Frequently Asked Questions
- 1. What do I need before I can login?
- 2. What is a secure shell (ssh)?
- 3. Is it really necessary for me to use secure shell for login?
- 4. How can I get a secure shell (ssh) client??
- 5. Can I connect with an XDM/CDE session?
- 6. How do I login and run X applications?
- 7. How do I tell if my X connection is tunneled?
You need an HPC account. See the Account Information page for detailed information on who is eligible for an account and how to get one.
You must follow UK and IT policies and procedures. See the UKIT Policies page.
You must use a secure shell (ssh) client to connect to the DLX cluster. See the Secure Shell page for more information.
The secure shell (ssh) is a means of encrypting your login session. See the Secure Shell page for more information.
Yes, it is very important to encrypt your login session, so that others cannot see your private information, especially your password. Unencrypted logins to the cluster are not allowed. See the Secure Shell page for more information.
Clients for ssh are available for all common operating systems, and many have the the client already built in. See the Secure Shell page for more information.
No, CDE sessions are not permitted for security reasons.
It is important for security reasons to use an encrypted X session, so that others cannot see your private information, especially your password. You will tunnel or tunnel your X connection through ssh. This depends on the proper client settings
On Linux, your client may be configured globally by default to set up forwarded X connections, or you may override the default with the -X command-line flag, or you may specify the tunnel on a per-host basis in your own configuration file. See the man ssh page on your Linux workstation.
On MS-Windows clients there is often a check-box in the session setup for X forwarding. This may be on a global basis or a per-host basis.
For more info about forwarding X11 connections with ssh clients, such as puTTY, see http://www.tldp.org/HOWTO/XDMCP-HOWTO/ssh.html. Note: this is an off-site link and could disappear without notice.
Check the DISPLAY variable to see if your X connection is being tunneled through ssh. If DISPLAY is set to a cluster node's IP number instead of your local workstation's IP number, then the connection is being tunneled. Use the command echo DISPLAY while connected to the cluster with X.