1.11.3 GNU/Linux

 As an Example of a free and open-source operating system, consider GNU/Linux. By 1991, the GNU operating system was nearly complete. The GNU Project had developed compilers, editors, utilities, libraries, and games - whatever parts it could not find dlsewhere. However, the GNU kernel never became ready for prime time. In 1991, a student in Finland, Linus Torvalds, released a rudimentary UNIX-like kernel using the GNU compilers and tools and invited contributions worldwide. The advent of the Internet meant that anyone interested could download the source code, modify it, and submit changes to Torvalds. REleasing updates once a week allowed this so-called "Linux" operating system to grow rapidly, enhanced by several thousand programmers. In 1991, Linux was not free software, as its license permitted only noncommercial redistribution. In 1992, however, Torvalds rereleased Linux under th GPL, making it free software (and also, to use a term coined later, "open source")

The resulting GNU/Linux operating system (with the kernel properly called Linux but the full operating system including GNU tools called GNU/Linux) has spawned hundreds of unique distributions, or cutom builds, of the system. Major distributions include Red Hat, SUSE, Fedora, Devian, Slackware, and Ubuntu. Distributions vary in function, utility, installed applications, hardware support, user interface, and purpose. For example, Red Hat Enterprise Linux is geared to large commercial use. PCLinuxOS-called PCLinuxOS Supergamer DVD - is a live DVD that includes graphics drivers and games. A gamer can run it on any compatible system simply by booting from the DVD. When the gamer is finished, a reboot of the system resets it to its installed operating system.

You can run Linux on a Windows(or other) system using the following simple, fre approach:

1. Downlaod the free Virtualbox VMM tool from

https://www.virtualbox.org/

and install it on your system.

2. Choose to install an operating system from scratch, based on an installation image like a CD, or choose pre-built operating-system images that can be installed and run more quickly from a site liek

http://virtualboxes.org/images/

These image are preinstalled with operating system and application and include many flavors of GNU/Linux.

3. Boot the virtual machine within Virtuallbox.

An alternative to using Virtualbox is to use the free program Qemu(http://wiki.qumu.org/Download/), which includes the qemu-img command for converting Virtaulbox images to Qemu images to easily import them.

With this text, we provide a virtual machine image of GNU/Linux running the Ubuntu release. This iamge contains the GNU/Linux source code as well as tools for software developement. We cover examples involving the GNU/Linux image throughout this text, as well as in a detailed case study in Chapter 20.