Accessing Clusters

In order to access your HPC account, you may need to generate an SSH key pair for authorization. You generate a pair of keys: a public key and a private key. The private key is kept securely on your computer or device. The public key is uploaded to the servers or systems that you want to access securely via SSH.

How do I generate an SSH key pair?¶

Windows Operating System¶

We recommend MobaXterm as the most straightforward SSH client. You can download its free home edition (Installer Edition) from https://mobaxterm.mobatek.net/ The Mobaxterm Portable Edition is not recommended as it deletes the sessions. Once you install the stable version of MobaXterm, open its terminal and enter this command:

ssh-keygen

This command will create a private key and a public key. Do not share your private key; we recommend giving it a passphrase for security. To view the .ssh directory and to read the public key, enter these commands:

ls -al ~/.ssh
more ~/.ssh/*.pub

MACOS:¶

Use a terminal to create an SSH key pair using the command:

ssh-keygen

To view the .ssh directory and to read the public key, enter these commands:

ls -al ~/.ssh
more ~/.ssh/*.pub

X11 Forwarding¶

Some software has a Graphical User Interface (GUI), and so requires X11 to be enabled. X11 forwarding allows an application on a remote server (in this case, Franklin) to render its GUI on a local system (your computer). How this is enabled depends on the operating system the computer you are using to access Franklin is running.

Linux¶

If you are SSHing from a Linux distribution, you likely already have an X11 server running locally, and can support forwarding natively. If you are on campus, you can use the -Y flag to enable it, like:

$ ssh -Y [USER]@[CLUSTER].hpc.ucdavis.edu

If you are off campus on a slower internet connection, you may get better performance by enabling compression with:

$ ssh -Y [USER]@[CLUSTER].hpc.ucdavis.edu

If you have multiple SSH key pairs, and you want to use a specific private key to connect to the clusters, use the otpion -i to specify path to the private key with SSH:-

$ ssh -i /path/to/private/key [USER]@[CLUSTER].hpc.ucdavis.edu

MacOS¶

MacOS does not come with an X11 implementation out of the box. You will first need to install the free, open-source XQuartz package, after which you can use the same ssh flags as described in the Linux instructions.

Windows¶

If you are using our recommend windows SSH client, MobaXterm, X11 forwarding should be enabled by default. You can confirm this by checking that the X11-Forwarding box is ticked under your Franklin session settings. For off-campus access, you may want to tick the Compression box as well.