There are several other implementations of UNIX for the 80386 and 80486. The 80386 architecture lends itself to the UNIX design, and a number of vendors have taken advantage of this.
Feature-wise, other implementations of UNIX for the PC are quite similar to Linux. You will see that almost all commercial versions of UNIX support roughly the same software, programming environment, and networking features. However, there are some strong differences between Linux and commercial versions of UNIX.
First of all, Linux supports a different range of hardware from commercial implementations. In general, Linux supports the most well-known hardware devices, but support is still limited to that hardware which developers actually have access to. However, commercial UNIX vendors generally have a wider support base, and tend to support more hardware, although Linux is not far behind. We'll cover the hardware requirements for Linux in Section 1.8.
Secondly, commercial implementations of UNIX usually come bundled with a complete set of documentation as well as user support from the vendor. In contrast, most of the documentation for Linux is limited to documents available on the Internet---and books such as this one. In Section 1.9 we'll list sources of Linux documentation and other information.
As far as stability and robustness are concerned, many users have reported that Linux is at least as stable as commercial UNIX systems. Linux is still under development, and certain features (such TCP/IP networking) are less stable but improve as time goes by.
The most important factor to consider for many users is price. The Linux software is free, if you have access to the Internet (or another computer network) and can download it. If you do not have access to such a network, you may need to purchase it via mail order on diskette, tape, or CD-ROM (see Appendix B). Of course, you may copy Linux from a friend who may already have the software, or share the cost of purchasing it with someone else. If you are planning to install Linux on a large number of machines, you need only purchase a single copy of the software---Linux is not distributed on a ``single machine'' license.
The value of commercial UNIX implementations should not be demeaned: along with the price of the software itself, one usually pays for documentation, support, and assurance of quality. These are very important factors for large institutions, but personal computer users may not require these benefits. In any case, many businesses and universities are finding that running Linux on a lab of inexpensive personal computers is preferrable to running a commercial version of UNIX in a lab of workstations. Linux can provide the functionality of a workstation on PC hardware at a fraction of the cost.
As a ``real-world'' example of Linux's use within the computing community, Linux systems have travelled the high seas of the North Pacific, managing telecommunications and data analysis for an oceanographic research vessel. Linux systems are being used at research stations in Antarctica. As a more mundane example, perhaps, several hospitals are using Linux to maintain patient records. It is proving to be as reliable and useful as other implementations of UNIX.
There are other free or inexpensive implementations of UNIX for the 386 and 486. One of the most well-known is 386BSD, an implementation and port of BSD UNIX for the 386. 386BSD is comparable to Linux in many ways, but which one is ``better'' depends on your own personal needs and expectations. The only strong distinction that we can make is that Linux is developed openly (where any volunteer can aid in the development process), while 386BSD is developed within a closed team of programmers who maintain the system. Because of this, serious philosophical and design differences exist between the two projects. The goals of the two projects are entirely different: the goal of Linux is to develop a complete UNIX system from scratch (and have a lot of fun in the process), and the goal of 386BSD is in part to modify the existing BSD code for use on the 386.
NetBSD is another port of the BSD NET/2 distribution to a number of machines, including the 386. NetBSD has a slightly more open development structure, and is comparable to 386BSD in many respects.
Another project of note is HURD, an effort by the Free Software Foundation to develop and distribute a free version of UNIX for many platforms. Contact the Free Software Foundation (the address is given in Appendix E) for more information about this project. At the time of this writing, HURD is still in early stages of development.
Other inexpensive versions of UNIX exist as well, such as Coherent (available for about $99) and Minix (an academic but useful UNIX clone upon which early development of Linux was based). Some of these implementations are of mostly academic interest, while others are full-fledged systems for real productivity. Needless to say, however, many personal UNIX users are moving to Linux.