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A Unix-like operating system is one that behaves in a manner similar to the UNIX system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification.The term is now most often used to refer to the Unix-like open source operating systems.
With the rise of Linux and its strong competitive showing against certified versions of Unix, Unix certification is becoming less relevant to the marketplace.
1 The term "Unix-like" and the UNIX trademark
The Open Group, which owns the UNIX trademark and administers the Single UNIX Specification, considers "UNIX-like" to be a usage problem, and believes that a better alternative term would be the term " POSIX-conforming system". However, the term "POSIX-conforming" has its own problems. For example, there are systems which conform to at least the key POSIX standards (e.g., Microsoft Windows) and can claim to be POSIX-conforming, but that are nevertheless not Unix-like and many applications written to compile and run on Unix will not work on them.
2 Early Unix-like systems
The first "Unix-like" operating systems were developed because of AT&T's licensing of Unix, which prevented the sale of Unix to commercial organisations. The Unix-like operating systems that were available in the 1980s and early 1990s included Idris, Coherent, UniFlex and Minix (a computer science teaching system).
When AT&T allowed Unix to be sold to commercial organisations in the 1980s, the market for the earliest Unix-like operating systems dried up. The rise of Linux in the 1990s killed the rest.
3 Unix-like open source operating systems
The term is most often used as a simple way of referring to the Unix-like open source operating systems:
- DarwinDarwin is the core operating system of Apple Computer's Mac OS X, and runs on an open source kernel called XNU. Darwin integrates a number of technologies, most importantly the Mach 3. 0 kernel, operating system services based on 4. 4 BSD (Berkeley Softwa
- FreeBSDFreeBSD is a Unix-like operating system descended from Unix via the BSD branch through 386BSD and 4. It runs on processors compatible with the Intel x86 family, as well as on the DEC Alpha, the UltraSPARC processors by Sun Microsystems, the Itanium (IA-64 and descendants:
- DragonFly BSDIn computing, the DragonFly BSD operating system is a fork of FreeBSD. Matt Dillon, a long-time FreeBSD and Amiga developer, started work on DragonFly BSD in June 2003 and announced it on the FreeBSD mailing lists on 16 July 2003. Dillon started DragonFly
- PicoBSDPicoBSD is a one floppy disk version of FreeBSD, one of the BSD operating system descendants. In its different variations, PicoBSD allows you to have secure dialup access, small diskless router or even a dial-in server, all on only one standard 1. 44MB fl
- TrustedBSDThe TrustedBSD project provides a set of trusted operating system extensions to the FreeBSD operating system, targeting the Common Criteria for Information Technology Security Evaluation (see also Orange Book). This project is still under development, and
- GNU/HurdGNU/Hurd or simply GNU is the common name of a free computer operating system consisting of the GNU system and the GNU Hurd kernel. The name is somewhat confusing since the GNU system includes GNU Hurd; however, it is used to distinguish it from GNU/Linux
- Linux
- Minix
- NetBSD
- OpenBSD and descendants:
