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Using GPG to Encrypt Your Data
Encryption helps protect your files during inter-host file transfers that use protocols that are not already encrypted—for example, when using ftp or when using shiftc without the secure option. We recommend using the GNU Privacy Guard (GPG), an...
03 Dec, 2025
Views: 279938
Commonly Used PBS Commands
The four most commonly used PBS commands, qsub, qstat, qdel, and qhold, are briefly described below. See man pbs for a list of all PBS commands. qsub To submit a batch job to the specified queue using a script: %qsub -q queue_name job_script ...
01 Sep, 2026
Views: 156081
Using MobaXterm for SSH Connections from Windows Systems to NAS
You can use MobaXterm to connect from your local Windows system to NAS systems via SSH, as an alternative to Cygwin/OpenSSH. MobaXterm includes a built-in X11 client, and has the ability to forward X11 from NAS systems back to your local system....
25 Mar, 2026
Views: 144398
Setting Up SSH Passthrough
NAS supercomputers are served by several front-end systems within the secure enclave. These include: Athena: athfe[01-04] Cabeus: cfe[01-02], cghfe[01-02] Aitken Milan: afe[01-02] Aitken Cascade Lake & Rome; Electra; Endeavour:...
25 Mar, 2026
Views: 129588
Lustre Best Practices
At NAS, Lustre (/nobackup) filesystems are shared among many users and many application processes, which can cause contention for various Lustre resources. This article explains how Lustre I/O works, and provides best practices for improving...
03 Dec, 2025
Views: 123855
Public/Private Key Pairs
Public-key authentication is a means of identifying yourself by proving that you know the private key associated with a given public key. This method is more secure than password authentication, but it requires more effort to set up. Public-Key...
19 Jan, 2018
Views: 107406
Commonly Used qsub Command Options
The qsub options can be read from the PBS directives of a PBS job script or from the qsub command line. For a complete list of available options, see man qsub. Commonly used options include: -S shell_name Specifies the shell that interprets the...
02 Dec, 2025
Views: 104164
Enabling Your RSA SecurID Hard Token (Fob)
If you are a new user logging in for the first time, complete steps 1–3 to enable your RSA SecureID fob, set up a personal identification number (PIN) for it, and change your default NAS password. If you are a current user and you just need to...
01 Jun, 2023
Views: 80157
Recommended Intel Compiler Debugging Options
Commonly Used Options for Debugging -O0 Disables optimizations. Default is -O2 -g Produces symbolic debug information in object file (implies -O0 when another optimization option is not explicitly set) -traceback Tells the compiler to...
29 Jun, 2015
Views: 76234
Enabling Your RSA SecurID Soft Token (Mobile App)
Once you enable your RSA SecurID soft token, you can log into the secure NAS enclave to set up a personal identification number (PIN) and change your default NAS password. Note: If you have a NAS-provided hard token (fob), see Enabling Your RSA...
01 Jun, 2023
Views: 74968
Shift Transfer Tool Overview
The NAS-developed Shift tool can copy files locally on NAS enclave hosts, transfer files between hosts inside the NAS enclave, and transfer files between the NAS enclave and remote hosts. You can also use Shift to check the status of transfers at...
20 Jul, 2020
Views: 70664
Common Login Failures or Issues
Use the information in this section to help troubleshoot any problems you encounter when logging into NAS systems. SSH Known-Hosts Error A successful host verification indicates that your Secure Shell (SSH) client has established a secure...
23 Jul, 2026
Views: 69469
VNC: A Faster Alternative to X11
Virtual Network Computing (VNC) software provides a way to reduce X11 overhead on high-latency networks such as the Internet. In practical terms, once a VNC session is underway, latencies are on the order of seconds rather than minutes. VNC can...
25 Mar, 2026
Views: 69290
Common Reasons Why Jobs Won't Start
If your job does not run after it has been successfully submitted, it might be due to one of the following reasons: The queue has reached its maximum run limit Your job is waiting for resources Your mission share has run out The system is...
01 Sep, 2026
Views: 67954
HPC Environment Overview
Our HPC environment is operated by staff in the NASA Advanced Supercomputing (NAS) Division at Ames Research Center located at Moffett Field, CA. The supercomputers and support staff are funded by NASA's High-End Computing Capability (HECC)...
01 Sep, 2026
Views: 66021
Lustre Basics
A Lustre filesystem is a highly scalable, high-performance shared filesystem for Linux clusters that is managed with Lustre software. It can support many thousands of client nodes, petabytes of storage, and hundreds of gigabytes per second of I/O...
03 Dec, 2025
Views: 65485
Basics on NVIDIA GPU Hardware Architecture
This article provides basic hardware architecture information to help you get familiar with the NVIDIA A100 and H100 graphics proessing units (GPUs) used in the NAS GPU nodes (mil_a100 and gh200). Refer to the official guides from NVIDIA listed in...
14 Sep, 2026
Views: 64754
Using Intel OpenMP Thread Affinity for Pinning
The Intel compiler's OpenMP runtime library has the ability to bind OpenMP threads to physical processing units. Depending on the system topology, application, and operating system, thread affinity can have a dramatic effect on code performance. We...
31 Dec, 2025
Views: 60149
Common Causes of Segmentation Faults (Segfaults)
A segmentation fault (often called a segfault) can occur if a program you are running attempts to access an invalid memory location. When a segmentation fault occurs, the program will terminate abnormally with an error similar to the following...
04 Dec, 2025
Views: 58176
PBS Job Queue Structure
Running Jobs on Athena To run a PBS job on the Athena compute nodes, submit the job from one of the Athena front-end systems (ATHFEs) to one of the queues managed by the PBS server pbs06a: devel, normal, long, and wide. Note: You cannot submit...
14 Oct, 2026
Views: 55583
Basic Tasks
Once you have completed preliminary tasks and read the Environment Overview, you can get started with using the supercomputers. The basic tasks below cover a typical user workflow cycle. Even these basic tasks require numerous setup steps...
14 Sep, 2026
Views: 54654
Cabeus GPU Nodes
Cabeus, named after a lunar crater in the south polar region of the Moon, is a cluster system that supports HPC and machine learning/artificial intelligence (ML/AI) applications that can benefit from the GPU technology. GPU Hardware Summary The...
13 Oct, 2026
Views: 49870
Using the Secure Unattended Proxy (SUP)
UPDATE: As of June 2, 2023, you must ensure that your SUP client has been updated with the latest version 8.13 (available below). You must do one of the following to replace their SUP client manually: Follow the installation instructions for the...
07 Oct, 2025
Views: 49642
HPE MPT
HPE's Message Passing Interface (MPI) is a component of the HPE Message Passing Toolkit (MPT), a software package that supports parallel programming across a network of computer systems through a technique known as message passing. MPT requires the...
30 Sep, 2021
Views: 49355
Portable Batch System (PBS): Overview
All NAS facility supercomputers use the Portable Batch System (PBS) from Altair for batch job submission, job monitoring, and job management. Note that different systems may use different versions of PBS, so the available features may vary slightly...
14 Sep, 2026
Views: 47121
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