Everyone knows that the Linux operating system was created from scratch about four years ago, right? Actually, while the Linux project is itself only four years old, it is important to remember that large parts of the Linux system on your desk are far older.

Linux is not an entire operating system—it is an operating system kernel. Any Unix or Unix-like operating system kernel requires a large suite of utility programs to complete the entire operating system. The Unix kernel has historically been distributed with many text manipulation tools, a C language compiler, programming libraries, and on-line documentation for all (or almost all) of the utilities and libraries. All of this together comprises the operating system.

Years before Linux was started, programmers who were fed up with bugs and limitations in the standard versions of Unix utilities started to write their own versions and contribute them to the Free Software Foundation's “GNU” project. Slowly, over the years, programmers noticed bugs and limitations in nearly all Unix utilities and wrote replacements for them, freeing the users from having to rely on software vendors to be consistently perfect.

These replacements were ported to most “flavors” of Unix that were available—but they all still required a commercial kernel, and the users were still dependent on their Unix software vendors to fix bugs and remove limitations in the kernel. The Free Software Foundation (known as the FSF) started work on a replacement kernel (now called “The Hurd”), but work was slow, original efforts met with legal challenges, and although the legal questions have long been settled, The Hurd has still not been publicly released.

In the spring of 1991, Linus Torvalds, a college student in Finland, started writing a 32-bit terminal emulator for his 386. He wrote it in a combination of assembly language and C, and in order to learn more about the 386 chip, made the emulator completely independent of DOS or any other operating system. Over the next few months, he learned enough to turn his terminal emulator into the beginnings of a Unix-like kernel.

To compile his code, Linus used the FSF's gcc C compiler and assembler. As a shell, he used the FSF's bash (“bourne again shell”). For the make program, he used the FSF's GNU make. In short, he and the team that quickly assembled around him used nearly all of the FSF's GNU programs to complement the Linux kernel and assemble a complete operating system.

These pre-tested and refined utilities turned a Unix-like kernel into a Unix-like operating system overnight. Many users who are not very familiar with the Free Software Foundation's suite of utilities are under the impression that the entire Linux operating system has been developed completely from scratch in the last four years. In reality, Linux leveraged (to use a current buzzword) a huge amount of tested, quality code to turn a kernel into an operating system, virtually overnight—the GNU project has enabled the Linux operating system to take the world by storm. Most of what's really new is the name and the kernel—much of the rest is GNU.

This does not belittle the kernel. It is large and complex, and there are few people who have the combination of qualities required to write—and especially maintain—one. It merely points out that Linux is in reality not a four-year-old newcomer, but a respectable, mature option for Unix users.

This new, powerful combination of the FSF's GNU utilities and the Linux kernel has in turn contributed to the quality of the GNU utilities. Because Linux users rely exclusively on the GNU utilities, when they find a bug in a GNU utility, they cannot simply fall back and use the version of the utility that came with the system. This means that more people are working on fixing those bugs that still exist in the GNU utilities, making them even more stable than they used to be. Those bug fixes (and enhancements) are usually given back to the FSF, as is appropriate.

Not all of the utilities that Linux uses come from the GNU project. The University of California at Berkeley had a long-running project which produced the Berkeley Software Distribution of Unix, known simply as BSD. Since much of the Unix networking software was developed by and for Bed's distribution of Unix, the BSD networking utilities still define the standards, and so many of the Linux networking utilities are time-tested utilities from BSD. As another example: thanks to the work done by MIT and the corporate members of the X Consortium, Linux had a well-tested, respected GUI less than a year after the project started.

Linux, as innovative as it is, has been created from “off-the-shelf” technology—it has gone fast and far on the shoulders of giants. It has employed (for the most part) proven technology to give users a truly open operating system.

The most important innovation Linux has given users is not the code, but the license. Because Linux is licensed under the FSF's GNU Public License, users have control, and are not tied to a vendor's apron strings. This creates a market for support, and users who are dissatisfied with the support they are receiving have the option to switch support providers. Not only is there a market for support, but users are also enabled to fix problems and enhance the software themselves, if they are so inclined.

Neither of those options truly exists for operating systems that do not include source; those options demonstrate the true innovation of Linux.