You can find Linux documentation in many books that have been written on the various distributions, or "flavors," of the Linux operating system. Some of these books have been chosen to serve as text books for classes taught by professors who provide additional documentation in the form of supplements to the text books that they have chosen. Online Linux communities and official websites dedicated to specific distributions provide Linux documentation and most distributions offer documentation in electronic format by including it on the installation compact discs (CDs) or digital versatile disk (DVD). Manual pages, more commonly known as "man" pages, provide extremely important documentation on programs and tools, and they are included with almost every version of every distribution.
There is a difference between official and unofficial Linux documentation. The unofficial versions, however, are not necessarily inferior or less complete than official ones that are provided with almost all supported or fee-based systems for production environments. It might even be said that Linux documentation is provided when working within a shell, also known as console-based work, because help is almost always available simply by typing a help command for particular Linux commands. One of the best sources for up-to-date information on the progress of written documentation for distributions in various languages is the Linux documentation project (LDD).
Books written on a specific distribution are generally considered the best non-electronic, offline sources for Linux documentation for various reasons. These books, if they are comprehensive, not only provide information on what programs and tools are available, they also provide information on the Linux operating system in general. Many of these books even provide an installation CD or DVD offering documentation in electronic format. This is especially useful for new users who need to grasp the very different concepts of Unix-based systems. Written instructions and explanations usually accompany photographs of screen shots so that step-by-step instructions can be followed.
Official websites and online technical help communities for specific distributions are excellent sources for Linux documentation because the websites reflect important information released by the developer of the distribution. That information is vital to writing accurate documentation. Online technical help communities are composed of computer programmers, experienced users of the distribution, inexperienced users and people who have experienced strange problems and found a solution for them. Such a variety of users means that you can probably find documentation not only for every release of the distribution but also for tips and tricks for solving hardware compatibility, network connection, security and software installation problems.