What is linux and why should we use it? Linux is a fast growing operating system, and it is inexpensive and flexible. Linux is also a major player in the small and mid-sized server field, and it’s an increasingly viable platform for workstation and desktop use as well. By understanding Linux, you’ll increase your standing in the job market... Linux is a clone of the UNIX operating system (OS) that has been popular in academia and many business environments for years. Formerly used exclusively on large mainframes, UNIX and Linux can now run on small computers. Because of its mainframe heritage, UNIX (and hence also Linux) scales well to perform today’s demanding scientific, engineering, and network server tasks. Linux consists of a Kernel, which is the core control software, and many libraries and utilities that rely on the Kernel to provide features with which user interact. The OS is available in many different distributions, which are collections of a specific Kernel with specific support programs. Command-Line Basics. Before you can do anything else with Linux, you should understand how to use a Linux shell. Several shells are available, but most of them provide similar capabilities. Understanding a few basics will take you a long way in your use of Linux, so I describe some of these techniques and commands. Linux Shell Options: Linux provides a range of options for shells. A complete list would be quite long so I only named the more common choices which include the following: bash – The GNU Bourne Again Shell (bash) is based on the earlier Bourne shell for UNIX but extends it in several ways. In Linux bash is the most common default shell for user accounts. bsh – The Bourne shell upon which bash is based also goes by the name bsh. It’s not often used in Linux, although the bsh command is usually a symbolic link to bash. tcsh – This shell is based on the earlier C shell (csh). It’s a fairly popular shell in some circles, but no major Linux distributions make it the default shell. It is similar to bash in many respects, some operational details differ. For instance, you don’t assign environment variables in the same way in tcsh as in bash. csh – The original C shell isn’t much used on Linux, but if a user is familiar with csh, tcsh makes a good substitute. ksh – The Korn shell (ksh) was designed to take the best features of bash and csh and extend them further. Its got a small but dedicated following among Linux users. zsh – The Z shell (zsh) takes shell evolution further than the Korn shell, incorporating features from earlier shells and adding still more. In addition to these shells, dozens more are available. Most users run bash because it’s the default. You can always see the shell commands by typing help. This was just a introduction to Linux shells, hope you understand the differences better now for those of you who never knew what a shell is.