What Is GNU/Linux?
GNU/Linux is a modular operating system that looks and acts like a more intelligently programmed, up-to-date Unix. The term itself -- GNU/Linux -- is extremely vague and doesn't exist in the literal sense. You don't go to the store and buy GNU/Linux; instead you buy a software distribution (or distro for short) that uses GNU/Linux as its basis. So while you can't buy "Linux" at the store, you can buy SUSE Linux or Linspire.
Distributions can fundamentally differ in several ways:
- Base operating system
- Software management and updating
- Hardware management
- Desktop environment and theme
- Proprietary extras
The sections below will cover each of these topics in depth. If there is one particular area that you are confused about, feel free to skip down to the appropriate section. The next topic will cover how GNU/Linux differs from Unix and other Unix-like operating systems.
BSD, Unix, OS X, Linux?
There are many Unix-like operating systems and derivatives. Which ones are which?
|Category||OSes||Origin of code?|
|GNU||GNU/Linux, GNU/HURD, GNU/Mach, GNU/BSD||Free Software Foundation; kernels developed separately except HURD. The Linux kernel was originally written by Linus Torvalds, and is currently maintained by him.|
|BSD||FreeBSD, OpenBSD, NetBSD, DesktopBSD, BSD/OS||UC Berkeley, originally; each project has been developed separately since the early-mid 1990s, however.|
|Unix||Solaris, AIX, IRIX, HP/UX, Tru64, UnixWare, OpenServer||Bell Labs (AT&T) developed the original Unix code. UNIX is now a trademarked operating system certification program instead of an operating system, and no longer requires that a compliant OS contain AT&T Unix source code to achieve brand certification. Despite that, all of the extant Unix derivatives are compliant with at least one published UNIX standard.|
|Darwin||Darwin, OS X||Based on the NeXTSTEP operating system, which used the Mach kernel and some FreeBSD programs and networking code. OS X is developed from Darwin.|
|Minix||Minix||Originally written by Andrew Tanenbaum, but now mostly developed by a handful of others|
GNU/Linux is only one possible combination of the GNU operating system with a separate kernel. GNU's own kernel is HURD, but it's been in development for a long time and is nowhere near ready for production. GNU/BSD and GNU/Mach exist, but more for experimental purposes than anything else. So in effect, GNU/Linux is the only GNU-based operating system that matters. Theoretically, you could use the operating system components from BSD and eliminate GNU entirely (or almost entirely) from GNU/Linux, but that would -- again -- be purely an academic pursuit.
Of the above-listed operating systems, only GNU/Linux has a variety of software distributions. The others are software distributions in themselves. The one exception is Solaris, which is based on code from the OpenSolaris project. There is at least one other OpenSolaris-based distribution aside from Solaris, and others are probably in development.
Most of these operating systems are similar in superficial ways. All are command line-based at heart, even if many of them default to graphical interfaces. Most of them share the majority of their terminal commands -- or have commands that have largely similar functionality and syntax -- so if you know one system very well, it is not difficult to learn a different one. GNU's userland utilities were improved replacements of Unix commands; BSD was originally developed from Unix source code, so its userland utilities started out as clones of Unix commands and have evolved from there. Some of these OSes can use the same software programs if properly configured. Some are restricted to specific hardware architectures, while others are extraordinarily versatile in terms of what computers they can operate on.
The amount of code- and program-sharing among all of these operating systems varies. All of them are guaranteed to have either BSD code integrated somewhere, or at least one GNU utility (usually the GNU Compiler Collection, the BASH terminal program, or the Emacs text editor, among many others) included by default.
Base operating system differences
Among GNU/Linux distributions, there can be many variances in the base operating system (kernel and userland utilities). Some have unique methods of managing startup scripts; others mimic BSD or Unix. You can know everything there is to know about creating and modifying init scripts on Red Hat Enterprise Linux, then be totally lost when trying to implement the same changes on Gentoo Linux.
Almost all distros make their own small, custom changes to the Linux kernel in order to accommodate other changes or additions that the distribution maintainers want to make. This makes each distro's kernel unique, and probably incompatible with other distributions. Commercial desktop GNU/Linux distros usually have extensively hacked kernels that support proprietary programs like Win4Lin, VMware, and proprietary hardware drivers.
GNU/Linux distributions are generally binary compatible with each other. That means that a program that will work on SUSE Linux will also work on Xandros and Linspire and any other distribution of the same generation and hardware architecture. Like all other operating systems, programs that are compiled for one architecture will not work on others. The only exception is 32-bit x86 binaries, which will work with most 64-bit AMD64 and Intel EM64T computers.
Software management and updating
Chances are, if you've selected the right GNU/Linux distribution for your needs, you won't have to add any extra software to it. If you do, most distros have software repositories that contain thousands of extra software packages that have been certified to work with your configuration. All you have to do is figure out which programs you want, select them from a list, and everything is installed for you. It's much like using Windows Update.
Also like Windows Update, all major GNU/Linux distributions come equipped with a software update framework. Unlike Windows Update, however, GNU/Linux updaters will find patches and bug fixes for all of the software on your computer -- not just the basic operating system. Each distribution has its own specialized update tools, but they are all generally easy to use.
On a more basic level, GNU/Linux distributions install software in one of two ways: by compiling from source code, or -- more commonly -- by installing precompiled binary packages.
Source-based distributions like Gentoo and Arch still have a software management framework like the big fancy commercial distros, but you have extra options. You can add in compiler flags to make programs a little faster or use less memory, or you can build applications with hooks to other programs so that your software is more interoperable. Binary distributions make guesses as to what your needs will be, and try to cover all of the bases by compiling everything in. In the real world, you're not going to notice much of a difference by adding compiler optimizations and other options, but if you like tinkering with your computer, you'll enjoy the experience.
Source-based distros will take a lot longer to manage because it takes time to compile large programs. You can use binary packages to get started, but updates are applied by compiling from source code. A binary installation of the KDE desktop environment takes only slightly longer than the time consumed downloading the binaries from the Internet, but compiling the full KDE system from source can literally take days. The same can be said of such behemoths as OpenOffice.org, GNOME, and Mozilla.
Binary distributions almost exclusively use two package formats for programs: RPM (a recursive acronym for RPM Package Manager), and DEB (short for Debian, a GNU/Linux distribution that is commonly used as a basis for others). In the old days, you may have had to go searching for RPMs or DEBs of programs that you wanted. In this day and age, however, you use your package manager to find and retrieve them for you. In the event that you must install one of these packages by hand, there are graphical alternatives to the standard command line tools for installing them. There are even tools available to use DEB packages on RPM-based distros, and vice-versa. Usually programs are packaged in both formats, though.
Red Hat (and Fedora Core), SUSE, and Mandriva are three well-known distributions that use RPM packages. Linspire, Xandros, Debian, Ubuntu, and Mepis are some of the most popular DEB-based distributions. Both package formats are heavily entrenched in these and other distributions; neither seeks to replace the other.
Occasionally you might see someone on a message forum or mailing list complaining about RPMs and "dependency hell." This is because individual packages usually depend on other packages, and that means tracking down several RPMs to install one program, then doing some command line kung-fu to install them in the right order. Again, this is the old way of doing things -- nowadays you let your package manager do the work for you.
Popular package managers include:
Commercial GNU/Linux distributions include software that automatically detects and installs the proper drivers for all of your computer hardware and peripherals. Usually it works perfectly without any user intervention necessary. Sometimes it encounters unsupported hardware, or hardware that requires a newer kernel or driver. Some distros share the same autodetection and hardware management code, some have a totally unique hardware management framework.
Non-commercial distros are usually good at detecting hardware, but never contain proprietary drivers for ATI and Nvidia video cards, some kinds of wireless network chips, RAID cards, and video capture cards. Drivers for these devices require licensing and distribution agreements that non-commercial distribution developers are generally unwilling to negotiate, agree to, or pay for. This means that if you want to take full advantage of your 3D graphics card, you will have to download and install a proprietary video driver. A simple Google search will usually yield installation instructions. Again, this is best done by adding software repository sources to your package manager instead of installing them by hand.
Desktop environments and themes
The two primary desktop environments in the world of GNU/Linux are GNOME and KDE. Most distros support both, and usually default to one or the other. There are also window managers, which don't have the large number of integrated programs, but are usually considered to be more responsive and efficient on slower computers. Which one you should use is entirely a matter of preference.
Aside from desktop environment, each distribution has its own special color, icon, login, desktop, and menu theme. You can change the theme -- there are several dozen good themes available, and more coming out every week -- so don't let the default look and feel of the desktop discourage you. You can make KDE look almost exactly like Windows XP, and you can make GNOME look almost exactly like Apple OS X. Window managers are even more customizable, but often require you to edit configuration files by hand.
In addition to the proprietary hardware drivers mentioned previously, there are also proprietary software extras that are an important complement to the desktop computing experience. Most people will, at one time or another, need to access a PDF, Java applet, Flash animation, or video file on the World Wide Web. And when they need to see those files, they need browser plugins to do it. Unfortunately, all of the most functional plugins for these technologies are not free-as-in-rights, and won't be included with the majority of GNU/Linux distributions. If you want them, you have to either choose a commercial distro (there are some recommendations in a section below), or add them by hand. As I've said before, adding them by hand is not necessarily difficult, but it will take some reading and research to get everything working perfectly. If you are not prepared to do this, do not choose a GNU/Linux distro that does not include these extras.
If you don't know what you're doing, don't choose distributions that require a lot of legwork to configure basic services or install extra software. If you are new to GNU/Linux and want a great desktop experience, I recommend trying these distros (listed in no specific order):
All of these distros will cost you something -- usually under US $100. A lot of experienced GNU/Linux enthusiasts will recommend non-commercial distributions like Ubuntu, Fedora Core, or Debian. These are good distros and are available free of charge, but require that you add proprietary video drivers and Web browser plugins by hand, and don't have the same kind of automatic hardware management that the four distros I listed above have. That means that you could end up rather frustrated by your GNU/Linux experience. Also stay away from the open source edition of SUSE Linux -- that is also missing many of the proprietary extras that you're used to in Windows or OS X (the commercial version of SUSE does have plugins for Java, Flash, and PDF). It's not tough to add them if you follow this guide, but many people are not prepared to get that technical with their software.
If you're looking for a distro that is more suited to server use, try these:
Again, people will argue that other distros or Unix-like OSes are better, but the above-mentioned distributions are easy to install, configure, and manage, and come with extensive documentation and commercial support. You will have a much easier time with them, and you're better off going with one of these if you're new to GNU/Linux or Unix-like operating systems in general. You can make virtually any GNU/Linux distribution into a server of any kind; it's just a matter of how much work you have to do to prepare and maintain it. If you don't want to do a lot of work, choose one of the above distros.
Non-commercial desktop distributions of note include:
If you would prefer more of a challenge, as either a server or a desktop OS, try these distros:
Lastly, if you would like to see what a GNU/Linux desktop can look like, you can download Knoppix, a distro that runs entirely from a CD. You write the ISO file to a blank CD-R disc, then restart your computer with the disc in the CD drive. You'll run a whole distribution right from the CD. When you're done playing around, just select the Shutdown menu option, remove the CD from the drive, and restart -- nothing will be written to your hard drive.