What is "illumos"

illumos is a free and open-source Unix operating system. It derives from OpenSolaris, which in turn derives from SVR4 UNIX and Berkeley Software Distribution (BSD). illumos comprises a kernel, device drivers, system libraries, and utility software for system administration. This core is now the base for many different open-sourced OpenSolaris distributions, in a similar way in which the Linux kernel is used in different Linux distributions.

The maintainers write illumos in lowercase since some computer fonts do not clearly distinguish a lowercase L from an uppercase i (see homoglyph). The name is derived from the Latin illuminare meaning " to enlighten," and "OS" for ' operating system'.