Linux is a kernel. Linux distributions bring together many components to create an operating system. In contrast, the four main flavours of BSD are complete operating systems; from the kernel to the system tools, everything is built by the same team. - FreeBSD - OpenBSD - NetBSD - DragonFlyBSD The eldest of the bunch is FreeBSD, and it is pure, unadulterated UNIX, unlike Linux, which is a UNIX clone; in fact, with systemd, it should no longer even be considered a UNIX clone, as it broke with the UNIX philosophy some time ago. For an IT professional, the first thing you notice when using FreeBSD is its consistency, reliability and excellent documentation compared to Linux. FreeBSD has always been part of my setups.