GNU/Linux

What is Linux?

Linux (properly GNU/Linux) has become so important in the Open Source world that it deserves a whole page to itself. Many people misunderstand what it is, where it comes from and where it fits into the whole picture so let's have some perspective on it.

Linux itself is an operating system. This means it is a piece of software that takes control of the bare hardware of the computer system, taking the disparate bits of ironmongery (network card, video card, disk drives, processor, memory and so on) and hiding them behind a standard set of software services. The reason you need an operating system is because 'real' software, the kind of stuff you probably want to run like your web browser, email, office suite, database and the rest does not want to know about the type of network card you have or whether your graphics card is on the PCI or AGP bus or other irrelevant detail. The operating system has the job of providing standardised interfaces which are independent of the hardware. It may do more besides but that is its main purpose.

If the operating system provides a standard set of services then the application software can be written so that it's almost wholly independent of the underlying hardware. That is precisely what not only GNU/Linux but also a host of related operating systems do. The standard that they mostly conform to is the single UNIX specification published and maintained by the Open Group.

All of the proprietary Unix distributions conform closely to the single UNIX specification, as do a number of Open Source initiatives that are not Linux. Examples of the latter include NetBSD, FreeBSD, OpenBSD and GNU Hurd, all of which have more or less diehard adherents. Much to the chagrin of those who love the alternatives, Linux is the one that gets the press and has caught the public imagination. If Linux hadn't been written then one of the alternatives could just as easily have taken its place.

Linux is purely the operating system. It runs on a wide range of hardware platforms ranging from handheld Personal Digital Assistants (PDA)s like the Sharp Zaurus, through innumerable mid-range desktop and server-style appliances, detouring via embedded systems up to high-end clusters and mainframes.

By itself an operating system is only useful for embedded devices like PDAs. Most users will want a whole set of supporting software like network administration, scheduling, scripting, language compilers, editors and a host of other utilities which allow you to perform general day-to-day administrative and configuration tasks. Linux is no different; a system that contains nothing but Linux will be suitable only for a very limited set of applications.

Where GNU comes in

Where Distributions come in

The bold and the brave can, if they want, download the source code of all of the components that go to make up a functioning system, picking from the GNU software, Linux or one of its alternates, Apache, Samba and the dozens of projects like them, then trying to make it all work together. As an act of grandeur it may be worth attempting but it is the software equivalent of scaling Everest. It is much easier to use a distribution where someone has already done that. Numerous vendors provide bundled packages of GNU, Linux and a wide assortment of other Open Source components already integrated. Not all of the distributions are commercial, for example Debian which is a community-maintained distribution with a vocal congregation.

If you can obtain these more or less free of charge (as the distributors are obliged to do, according to the licences for most of the Open Source packages), why would you pay for a distribution? This question has vexed the main commercial suppliers of packed GNU/Linux and they have come up with a number of answers. The first is to obtain support: a commercial GNU/Linux distribution normally includes pre-paid support plus the option to purchase ongoing support. For commercial users this is entirely normal practice and not a difficult case to make. The second argument is one of certification. If you want to run a supported non Open Source package like Oracle then it is most likely intended for mission-critical work. You will want the application to be properly supported by its vendor, but that vendor will only certify it on a carefully tested platform. That's where certified GNU/Linux distributions come in. You may be able to download the identical distribution from the vendor's website free of charge, but for the certification you have to pay.

Both forms are available from the mainstream GNU/Linux commercial suppliers. Some strapped-for-cash users have noted that they can probably pay for the certified version where necessary yet run the identical version of the software on less critical systems without certification, provided they only use the packages which conform to the free of charge licences.

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