Oracle Solaris

Oracle Solaris is a proprietary Unix operating system offered by Oracle for SPARC and x86-64 based workstations and servers. Originally developed by Sun Microsystems as Solaris, it superseded the company's earlier SunOS in 1993 and became known for its scalability, especially on SPARC systems, and for originating many innovative features such as DTrace, ZFS and Time Slider. After the Sun acquisition by Oracle in 2010, it was renamed Oracle Solaris.

Solaris was registered as compliant with the Single UNIX Specification until April 29, 2019. Historically, Solaris was developed as proprietary software. In June 2005, Sun Microsystems released most of the codebase under the CDDL license, and founded the OpenSolaris open-source project. Sun aimed to build a developer and user community with OpenSolaris; after the Oracle acquisition in 2010, the OpenSolaris distribution was discontinued and later Oracle discontinued providing public updates to the source code of the Solaris kernel, effectively turning Solaris version 11 back into a closed-source proprietary operating system. Following that, OpenSolaris was forked as Illumos and is alive through several Illumos distributions. In September 2017, Oracle laid off most of the Solaris teams.

In 1987, AT&T Corporation and Sun announced that they were collaborating on a project to merge the most popular Unix variants on the market at that time: Berkeley Software Distribution (BSD), UNIX System V, and Xenix. This became Unix System V Release 4 (SVR4). About 40 AT&T and Sun programmers would work together in the San Francisco Bay area, the two companies said, with the goal of SunOS compliance with SVR4 in 1988 and addition of BSD 4.2 features in 1989.

On September 4, 1991, Sun announced that it would replace SunOS 4, with one based on SVR4. This was identified internally as SunOS 5, but a new marketing name was introduced at the same time: Solaris 2. The justification for this new overbrand was that it encompassed not only SunOS, but also the OpenWindows graphical user interface and Open Network Computing (ONC) functionality.

Although SunOS 4.1.x micro releases were retroactively named Solaris 1 by Sun, the Solaris name is used almost exclusively to refer only to the releases based on SVR4-derived SunOS 5.0 and later.

For releases based on SunOS 5, the SunOS minor version is included in the Solaris release number. For example, Solaris 2.4 incorporates SunOS 5.4. After Solaris 2.6, the 2. was dropped from the release name, so Solaris 7 incorporates SunOS 5.7, and the latest release SunOS 5.11 forms the core of Solaris 11.4.

Although SunSoft stated in its initial Solaris 2 press release their intent to eventually support both SPARC and x86 systems, the first two Solaris 2 releases, 2.0 and 2.1, were SPARC-only. An x86 version of Solaris 2.1 was released in June 1993, about 6 months after the SPARC version, as a desktop and uniprocessor workgroup server operating system. It included the Wabi emulator to support Windows applications. At the time, Sun also offered the Interactive Unix system that it had acquired from Interactive Systems Corporation. In 1994, Sun released Solaris 2.4, supporting both SPARC and x86 systems from a unified source code base.

In 2011, the Solaris 11 kernel source code leaked.