Logging in to Hopper
You can log in to Hopper using SSH (Secure Shell) with the following command from any UNIX, Mac OS X, Linux, FreeBSD, etc. command shell or terminal:
ssh -l username hopper.nersc.gov
There are several SSH-capable clients available for Windows, Mac, and UNIX/Linux machines. NERSC does not support or recommend any particular client.
Hopper has 12 login nodes. You will be randomly connected to one of those 12 when you ssh to hopper.nersc.gov. In all cases it will appear to you as if you are on "hopper.nersc.gov."
The login nodes are where you compile codes, submit jobs, and view data. The login nodes on Hopper are "external," meaning they are not directly connected to Hopper's internal high-speed "Gemini" network. Because the login nodes are external you can log in and work with data and files when the main system is undergoing maintenance.
Please do not execute long-running applications on the login nodes. Instead, use a batch script and submit it so that the applications run on the Hopper compute nodes.
Accelerated X11 Performance
NX is a freely available software package that greatly improves X11 performance over the wide area network. NERSC recommends NX for those having X11 performance issues when running X applications at NERSC. See the "Connecting to NERSC" link in the right sidebar of this page for more information.