Online version of the book published in 2005 by Alexey Fedorchuk. Accessible UNIX. Linux, FreeBSD, DragonFlyBSD, NetBSD, OpenBSD. BHV - St. Petersburg, 2006, 672 pp. The book is devoted to the description of free POSIX-compatible (or Unix-like) operating systems, representatives of which are Linux, FreeBSD and other members of the BSD family, as well as their use as a universal platform of common ( including home) purposes. The presentation is not tied to any specific OS or distribution, but contains a description of the general principles of installation, configuration and use of any of the representatives of this family. The author refuses the linear scheme of presentation of the material, traditional for “paper” publications. The main storyline (chapters of the book) contain the general principles of the design of POSIX-compatible systems and work in them. It is aimed at a wide range of curious users, including beginners with no experience in Unix and Linux. The book's chapters alternate with interludes detailing the general material and illustrating it with examples from specific systems and distributions. They require some preliminary preparation (to the extent of the general part) and may be of interest to “current” users of free Unix-like operating systems.