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illumos is a collection of software that forms the core of an Operating System. It includes the kernel, device drivers, core system libraries, and utilities. Conceptually, the illumos idea of "the operating system" lies between something like Linux (which is the kernel only; all of userspace is delivered by vendors in a "distribution") and the BSD family of operating systems, which are packaged as a complete unit (kernel, core libraries, userspace utilities, and even end-user software packages).
illumos is the home of many technologies including ZFS, DTrace, Zones, ctf, FMA, and more. We pride ourselves on having a stable, highly observable, and technologically different system. Finally, illumos has a proud engineering heritage, tracing it roots back through Sun Microsystems to the original releases of UNIX and BSD.
Last modified 23 August 2025