The systems in the computer modeling laboratory, as well as Tennessee Tech University’s HPC cluster, run versions of the Linux operating system. Linux is a family of open-source, UNIX-like operating systems that are based on the Linux kernel. UNIX is a family of multi-tasking, multi-user operating systems that run on most of the internet servers and scientific computing clusters in the world today. The most popular commercially-available UNIX operating system today is Mac OS X. Many smartphones and tablets, including the iPhone, iPad and Android devices, are running a UNIX-based operating system as well.
The development of UNIX pre-dates Windows by at least a decade, going back to the original AT&T UNIX developed at Bell Labs in 1970. AT&T licensed UNIX to outside parties in the late 1970s, which led to a variety of academic and commercial variants — University of California at Berkeley (BSD UNIX), Microsoft (Xenix), Sun Microsystems (SunOS/Solaris), HP UNIX (HP-UX), and IBM (AIX). Today’s Mac OS X is based off of the NeXTSTEP/OPENSTEP UNIX variant, which is a derivative of BSD UNIX. UNIX systems are commonly characterized by their modular design which is often referred to as the, “UNIX philosophy.” This idea is that the operating system should provide a set of simple tools which individually perform a limited, well-defined function. Scientists in 1970 never envisioned that computers would one day occupy a desktop (or even someone’s pocket, for that matter), so it was essential that a multi-user operating system be developed with a unified filesystem and inter-process communication. A system of shell-scripting and command language, known as the UNIX shell, was developed to provide tools for complicated workflows.
Linux was developed separately in the late 1979s by Finnish-American software engineer, Linus Torvalds, with the first Linux kernel becoming available on September 17, 1991. It was originally developed for personal computers based on the Intel x86 architecture. Many Linux distributions and supporting software and libraries are provided under an open source license through the GNU Project. Due to the open source nature of Linux, the operating system has become popular among the scientific computing community and is the primary operating system used by the majority of high performance computing (HPC) clusters and supercomputers.
Most modern MacOS X and Linux workstations today come with a graphical user interface (GUI) to simplify the use of the computer as much as possible. To take full advantage of the scripting capabilities for automating tasks and analyzing complicated scientific data, some knowledge of the command prompt is necessary. Most of the commands are very short and simple, such as ‘ls‘ for obtaining a listing of files in your directory, ‘cd‘ for changing directories, or ‘rm‘ for removing files. For novice users, it might be helpful to download the following “cheat sheets”, containing many commonly used UNIX commands: