OpenServer
SCO OpenServer 5.0.7 running theX.desktop interface
Developer	SCO,Caldera Systems,Caldera International,The SCO Group,Xinuos
OS family	UNIX System V (SVR3.2/SVR5),BSD
Working state	Current
Source model	Closed source
Initial release	1989; 36 years ago (1989)
Latest release	OpenServer 6 Definitive 2018 SVR5 / 2017; 8 years ago (2017)
Supported platforms	IA-32
Kernel type	Monolithic kernel
Userland	POSIX /SUS
License	Proprietary
Preceded by	Xenix
Official website	OpenServer 6 OpenServer 5

Xinuos OpenServer, previouslySCO UNIX andSCO Open Desktop (SCO ODT), is a closed source computeroperating system developed bySanta Cruz Operation (SCO), later acquired bySCO Group, and now owned byXinuos. Early versions of OpenServer were based onUNIX System V, while the later OpenServer 10 is based onFreeBSD 10. However, OpenServer 10 has not received any updates since 2018 and is no longer marketed on Xinuos's website, while OpenServer 5 Definitive and 6 Definitive are still supported.

In 1987AT&T Corporation,Microsoft, andSun Microsystems agreed to combine their versions of theUnix operating system.Santa Cruz Operation (SCO) sublicensed Microsoft'sXenix and wanted to retain the Xenix name, but AT&T said "If they want to call it Unix, they've got to use it the way it is. We don't want another set of variants".^[1]

SCO UNIX was the successor to Xenix, derived fromUNIX System V Release 3.2 with an infusion of Xenix device drivers and utilities. SCO UNIX System V/386 Release 3.2.0 was released in 1989, as the commercial successor to SCO Xenix. The base operating system did not includeTCP/IP networking orX Window System graphics; these were available as optional extra-cost add-on packages. Shortly after the release of this bare OS, SCO shipped an integrated product under the name of SCO Open Desktop, or ODT. 1994 saw the release of SCO MPX, an add-onSMP package.

At the same time, AT&T completed its merge of Xenix,BSD,SunOS, andUNIX System V Release 3 features intoUNIX System V Release 4. SCO UNIX remained based on System V Release 3, but eventually added home-grown versions of most of the features of Release 4.

The 1992 releases of SCO UNIX 3.2v4.0 and Open Desktop 2.0 added support for longfile names andsymbolic links. The next major version, OpenServer Release 5.0.0, released in 1995, added support forELF executables and dynamically linkedshared objects, and made many kernel structures dynamic.

SCO OpenServer 5, released in 1995, would become SCO's primary product and serve as the basis for products like PizzaNet (the first Internet-based food delivery system done in partnership withPizza Hut) and SCO Global Access, an Internet gateway server based on Open Desktop Lite.^[2] To compete withWindows NT andLinux, by 1997 SCO was distributing single-user licenses for educational use for $19, the cost of the CD-ROM, or completely free at trade shows.^[3] Due to its large installed base, SCO OpenServer 5 continues to be actively maintained by SCO with major updates having occurred as recently as September 2018.^[4]

SCO OpenServer 6, based on the merging of Openserver 5 and large portions of Unixware 7 was initially released byThe SCO Group in 2005. It includes support for large files, increased memory, and multi-threaded kernel (light-weight processes). This merged codebase isUNIX System V Release 5 (SVR5) of which the original version is seen in Unixware 7; SVR5 is only used byXinuos. SCO OpenServer 6 contains theUnixWare 7's SVR5 kernel integrated with SCO OpenServer 5 application and binary compatibility, OpenServer 5 system administration, and OpenServer 5 user environments.Unixware 7 was ironically based on a merger of AT&TUNIXSystem V Release 4.2MP (Unixware 2) and select technologies from OpenServer 5.^[5]

SCO OpenServer has primarily been sold into the small and medium business (SMB) market. It is widely used in small offices,point of sale (POS) systems, replicated sites, and backofficedatabase server deployments. Prominent larger SCO OpenServer customers includeMcDonald's,Taco Bell,Big O Tires,Pizza Hut,Costco pharmacy,NASDAQ, TheToronto Stock Exchange,Banco do Brasil, many banks inRussia andChina, and the railway system ofIndia.^[6][7][8]

SCO purchased the right to distribute theUnixWare system and its System V Release 4 code base fromNovell in 1995. SCO was eventually able to re-use some code from that version of UnixWare in later releases of OpenServer. Until Release 6, this came primarily in the compilation system and theUDI driver framework and theUSB subsystem written to it.

SCO announced on August 2, 2000, that it would sell its Server Software and Services Divisions, as well as UnixWare and OpenServer technologies, toCaldera Systems, Inc. The purchase was completed in May 2001. The remaining part of the SCO company, the Tarantella Division, changed its name toTarantella, Inc., while Caldera Systems becameCaldera International, and subsequently in 2002, theSCO Group.

The SCO Group continued the development and maintenance of OpenServer. On June 22, 2005, OpenServer 6.0 was released, codenamed "Legend", the first release in the new 6.0.x branch. SCO OpenServer 6 is based on the UNIXSystem V Release 5 kernel, a merged codebase ofUNIX System V Release 4.2MP andUnixWare 7. OpenServer 6.0 features multi-threading application support for C, C++, and Java applications through the POSIX interface. OpenServer 6 features kernel-level threading (not found in 5.0.x).

Some improvements over OpenServer 5 include improved SMP support (support for up to 32 processors), support for files over a terabyte on a partition (larger network files supported through NFSv3), better file system performance, and support for up to 64GB of memory.

OpenServer 6.0 maintains backward-compatibility for applications developed for Xenix 286 onwards.^[9]

The SCO Group went bankrupt in 2011, after a longseries of legal battles.

The rights to OpenServer, as well as UnixWare, were acquired by UnXis in 2011, which was later renamedXinuos.

In June 2015, Xinuos announced OpenServer 10, which is based on theFreeBSD 10 operating system. Simultaneously, Xinuos introduced a migration path for existing customers using older OS products. In December 2015, Xinuos released "definitive" versions of OpenServer 5, OpenServer 6, and UnixWare 7.

In December 2017, Xinuos released "Definitive 2018" versions of OpenServer 6 and UnixWare 7, and in October 2018 OpenServer 5 Definitive 2018 was released. The "Definitive 2018" releases were a commitment by Xinuos to keep the legacy OS's updated and supported protecting the applications that customers need to continue to run. The Definitive 2018 products contain major updates over the Definitive releases, and an updated development kit was released which makes it easier to compile current packages for the Definitive 2018 products.

However, by 2023, OpenServer 10 was no longer listed as a product on Xinuos' home page, implying that it had been withdrawn from marketing.^[10]

• Santa Cruz Operation
• SCO v. Novell
• SCO Skunkware

• SCO OpenServer 6.0 (deprecated) home page
• SCO OpenServer 5.0.7 (deprecated) home page
• SCO OS FAQ (3.2v4.2 and 3.2v5.0.x)

• FreeBSD
• UNIX System V
• X86 operating systems

• CS1: unfit URL
• Articles with short description
• Short description is different from Wikidata