An operating system is said to be Unix-based or Unix-like if it's designed to function and behave similar to the Unix operating system. Examples of proprietary Unix-like operating systems include AIX, HP-UX, Solaris, and Tru64.

The phrase "Unix-like operating system" is meant to exclude Unix operating systems such as Sun's Solaris and HP's HP-UX because they, as well as others, are compliant with one of the UNIX...

When we call an OS “Unix-like,” that generally will mean that the source code of the OS (the version of the software as it was originally coded) is directly traceable to, has similar properties to, and is explicitly based on Unix. Examples are Compaq’s True64, Solaris, IRIX, HP-UX, and IBM’s AIX.

*A Unix-like (sometimes shortened to nix to circumvent trademark issues) operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification.

GNU/Linux, FreeBSD, and OpenBSD are probably your best bets out of the 12 options considered. "A wide variety of distributions available" is the primary reason people pick GNU/Linux over the competition. This page is powered by a knowledgeable community that helps you make an informed decision.

In that sense, Linux is a UNIX-like, not a UNIX-based, operating system. In other words, Linux was influenced by UNIX, but UNIX systems have no relation to Linux. With that said, here are some of the more important UNIX systems that still exist today and are worth knowing about.

Unix-like operating systems: These look and operate like Unix, but haven’t been certified as compliant. It’s entirely possible, of course, that some operating systems in the “Unix-like” category could be tested tomorrow and found compliant.