Solaris to illumos: how the fork survive

Wetin Solaris and illumos be

Solaris and illumos na two branches from one Unix source tree. Sun Microsystems build Solaris and publish most of the source code for am in 2005. Oracle buy Sun for 2010 and stop publishing that source, so developers outside Oracle carry the open code go forward under new name: illumos. The operating system itself na niche for 2026. The storage layer and tracing tool wey dem build inside am no be niche, and na why this history worth your time.

If you run ZFS for Linux or FreeBSD, you dey run code wey dem write for Sun for Solaris, and wey outlive the company, the product line, and the licence fight. This post na the story of how e happen, with the dates checked.

Solaris wey come from: BSD, System V and SVR4

Sun Microsystems start on 24 February 1982. Scott McNealy, Andy Bechtolsheim, Vinod Khosla and Bill Joy na dem found am. Its operating system, SunOS, come from BSD (Berkeley Software Distribution), wey be the university Unix line wey Bill Joy work on before Sun exist. The other Unix line na AT&T's System V, wey dem dey sell commercially. Na these two branches the Unix family tree wey end with Linux describe, and Sun dey for the BSD side for ten years.

For 1987, Sun and AT&T announce joint project to merge BSD, System V and Xenix into one release: UNIX System V Release 4, wey people usually write as SVR4. On 4 September 1991, Sun announce say SunOS 4 go replace with SVR4-derived system under new marketing name, Solaris 2. Solaris 2.0 release for June 1992, and e work for SPARC hardware only. Sun don change side for the Unix split, and its customers need port their software.

The old name no ever disappear. The kernel keep the SunOS numbering, so Solaris 2.6 run SunOS 5.6, and Oracle Solaris 11.4 still report itself as SunOS 5.11. Run uname -a for illumos machine in 2026, and the first word wey e print still be SunOS, because illumos inherit the name together with the code.

Wetin Solaris 10 introduce for 2005

Solaris 10 release on 31 January 2005. E matter here because everything wey survive the company dey inside that release or come with one of its updates.

Bryan Cantrill, Mike Shapiro and Adam Leventhal write DTrace for Sun, and e first become available for November 2003. E instrument running kernel and running user processes without recompiling anything and without restarting the process wey you dey watch. Probe wey you never enable no cost anything, because dem patch the instrumentation in only when script ask for am. Na why administrators fit use am for production machines. DTrace win the top prize for The Wall Street Journal's 2006 Technology Innovation Awards, and one USENIX STUG (Software Tools User Group) award for 2008.

Jeff Bonwick, Bill Moore and Matthew Ahrens design ZFS for Sun, and dem announce am on 14 September 2004. E merge volume manager and filesystem into one layer. Na this make e fit checksum every block when e read am and repair bad block from redundant copy. Writes dey use copy on write: block no dey overwrite for the same place. So, if system crash for middle of write, old data remain intact instead make filesystem half-written. Snapshots cost almost nothing because snapshot na simply the set of blocks wey later writes never touch. ZFS no dey inside the first Solaris 10 release. E ship for Solaris 10 6/06 update, for June 2006.

Zones na the third part. Zone give one kernel several isolated user spaces. Each one get its own root filesystem, process table and network configuration. Zones appear for one Solaris 10 beta build for February 2004 and ship with the full release. FreeBSD reach the same idea earlier through another direction, and the comparison between jails and Docker containers still be the clearest way to understand wetin kernel level isolation really be. Zones still dey alive for illumos today, and dem be the foundation of at least one distribution wey come later.

Why Sun open the Solaris source code

Sun submit the CDDL (Common Development and Distribution License) to OSI (Open Source Initiative) on 1 December 2004, and OSI approve am on 14 January 2005. CDDL base on version 1.1 of MPL (Mozilla Public License). The copyleft work for each individual file: CDDL source file must remain CDDL, but binary wey dem build from am fit combine with code wey use other terms.

DTrace go first. Dem release the source under CDDL on 25 January 2005, for the newly launched opensolaris.org site, six days before Solaris 10 itself release. Most of the Solaris system code follow on 14 June 2005. ZFS enter the main Solaris development trunk on 31 October 2005 and reach OpenSolaris developers for build 27 on 16 November 2005. OpenSolaris later become distribution wey you fit install: 2008.05 arrive on 5 May 2008 as live CD, and 2009.06 arrive on 1 June 2009 with SPARC support.

The licence choice still decide wetin you fit run today. Free Software Foundation classify CDDL as free software licence wey no compatible with GPL (GNU General Public License), and this incompatibility come from MPL 1.1. Linux kernel na GPLv2. Na why ZFS on Linux dey build as kernel module outside the kernel source tree instead of merging am into the kernel, and why e no dey inside the mainline kernel. The decision to publish under any open licence na the one wey matter pass for the rest of this story, and the history of open source licensing explain why company fit decide to do am at all.

Wetín happen when Oracle buy Sun

Oracle announce for 20 April 2009 say e go buy Sun for US$7.4 billion, or US$5.6 billion after dem remove Sun cash and debt. Dem complete the deal for 27 January 2010.

For 13 August 2010, internal Oracle memo wey Mike Shapiro, Bill Nesheim and Chris Armes write circulate inside the company, then e leak. E state the new policy directly: "We will no longer distribute source code for the entirety of the Solaris operating system in real-time while it is developed, on a nightly basis." E rule out any more community builds: "We will not release any other binary distributions, such as nightly or bi-weekly builds of Solaris binaries, or an OpenSolaris 2010.05 or later distribution." Instead, open source releases go follow products wey dem release: "We will distribute updates to approved CDDL or other open source-licensed code following full releases of our enterprise Solaris operating system."

For 23 August 2010, OpenSolaris Governing Board pass resolution wey record say Oracle never appoint liaison to the board and say e don announce the end of the development partnership for 13 August. The board vote to return control of the community to Oracle under the charter wey Sun originally write. This dissolve the board.

Oracle Solaris 11 release for 9 November 2011. For 2 September 2017, Oracle lay off most of the Solaris teams. Oracle Solaris 11.4 release for 28 August 2018, and na still the current release. Under Oracle lifetime support policy, Premier Support for 11.4 go reach November 2031, while Extended Support go reach November 2037. So, Solaris na supported commercial product with published end date, for release wey don remain current since 2018.

How illumos start, and why dem call am fork

For 3 August 2010, ten days before dem leak the memo, Garrett D'Amore announce illumos. The name join illum, Latin word for light, with OS for operating system, and the project dey write am as one word with only the first letter capitalised.

The target na OS/Net, wey dem usually write as ON: the consolidation wey hold the kernel and the core system utilities. OpenSolaris never fully open. Some parts ship as closed binaries wey nobody outside Sun fit rebuild, including the internationalisation code inside the C library (libc_i18n), the NFS lock manager, the cryptographic framework, drivers like the mpt driver for LSI host bus adapters, and some SPARC platform code. Replacing dem na the project first job, because operating system wey you no fit build from source no be one wey you fit maintain.

D'Amore dey careful with the word fork. "We no be fork today, because of how we track OS/Net," he write, describing a downstream repository wey go follow Oracle tree and fit send changes back upstream. Ten days later, the upstream stop publishing. illumos become fork by default, because nothing remain to track. The core tree, illumos-gate, don pass 23,000 commits as of August 2026 and e still dey receive more.

Which distributions come from illumos

illumos no be something wey you install. Na the core tree, and distributions dey build usable system on top of am. Na these ones still dey release.

• OpenIndiana formally launch on 14 September 2010 for JISC Centre for London, and na the closest descendant of the old OpenSolaris desktop and server distribution. Na rolling release wey dem name Hipster, and dem publish the 2026.04 snapshot on 5 May 2026.
• OmniOS na server distribution. Now na the community dey maintain am as OmniOS CE after the original vendor stop work on am.
• SmartOS na hypervisor platform wey dem build on zones. Joyent create am and announce for April 2022 say SmartOS and Triton dey move go MNX Solutions, effective 1 May 2022.
• NexentaStor use the same base for storage appliances. Na the commercial line illumos come from.
• Tribblix na small distribution wey Peter Tribble dey maintain, as we explain below.
• DilOS put Debian package tooling on top of illumos kernel.

Wetin installing an illumos system look like today

Tribblix na useful example because e small, dem document am publicly, and dem still dey release am. Dem publish Milestone 41 for x86 on 5 August 2026, and the SPARC line reach Milestone 34 on 21 April 2026. The project describe itself as retro style with modern components, and e keep the SVR4 package format wey Solaris use instead of moving go newer package system.

The install dey run from live image. You boot the ISO, log in as user jack with password jack, become root, then run the installer against disk device. Na this command the project own install documentation give:

./live_install.sh -G c1t0d0

The -G flag dey write EFI (extensible firmware interface) partition layout, while -b select legacy MBR (master boot record) layout instead. Disk names follow Solaris cXtYdZ convention instead of /dev/sda. Na the first thing wey go look unfamiliar if you come from Linux. Software sets dey called overlays, and you fit name dem for the same line:

./live_install.sh -G c1t0d0 develop desktop

After installation, the package tool na zap. E dey work on overlays so dependencies fit dey handled for you:

zap refresh
zap install-overlay develop
zap update-overlay -a

Na these commands Tribblix publish. Dem dey run for hardware or hypervisor wey you control. You no go find dem behind one-click image for VPS control panel. That gap na the honest state of illumos deployment for 2026.

Why ZFS and DTrace outlived Solaris

ZFS comot from Solaris almost immediately after dem publish the source. Pawel Jakub Dawidek port am go FreeBSD, where e don dey part of the system since FreeBSD 7.0 for 2008. Native ZFS work for Linux start for 2008 and produce the first stable release for 2013. Between 2010 and 2013, illumos hold the reference copy of the ZFS source, because Oracle tree dey closed and every other port need place to pull from. Na this be the concrete value of the fork: without am, the ports no go get common ancestor to merge against.

Dem announce the OpenZFS project on 17 September 2013 to coordinate those ports. Matt Ahrens, one of the original ZFS authors, dey among the founders. OpenZFS 2.0 release on 30 November 2020, and the release notes talk the result clearly: "The ZFS on Linux project has been renamed OpenZFS! Both Linux and FreeBSD are now supported from the same repository making all of the OpenZFS features available on both platforms." FreeBSD 13.0 remove its own illumos-derived copy and move go that shared tree.

The two ZFS lines don diverge for disk. The open line stop for pool version 28, the last version wey Sun publish, then move go named feature flags under placeholder version 5000. This one mean say pool dey advertise the features wey e use instead of one number. Oracle continue incrementing its own version numbers behind closed source. Pool wey you create past version 28 for one side no fit import for the other side. If you dey choose where to run am, how OpenZFS dey behave for FreeBSD compared with Linux cover wetin really differ between the two hosts.

DTrace travel shorter distance. E don be standard for FreeBSD by 7.1 for January 2009, and Apple add am to Mac OS X 10.5 Leopard. Oracle release the DTrace kernel code under GPLv2 for August 2017. Plenty people notice the change for February 2018, and e remove the licence barrier to Linux. Dem never merge am into the mainline kernel. Linux tracing for practice dey run on eBPF, and bpftrace give am scripting language wey deliberately dey close to DTrace D.

The general point na the pattern, no be Solaris matter. Sun publish ZFS and DTrace under licence wey allow other people keep copy and continue work on am. When the company wey pay for the work stop, the work continue because the code don already dey for other trees and other people hands. The parts of Solaris wey dem never open, including the closed binaries wey illumos need rewrite, follow the company comot. Na this open sourcing dey change, and na the same mechanism dey behind how Linux distributions dey descend from one another.

You suppose run illumos for VPS?

For almost everybody, the answer na no, and nothing wey dey above na recommendation to try am. illumos support small range of hardware, because na the drivers wey Sun support plus the ones wey small community write since dey make up its driver set. VPS providers dey publish Linux and BSD images, so illumos installation usually mean say you go upload your own ISO to provider wey allow custom images, then check whether e recognise the virtual disk and network devices. Third-party software dey come from the distribution own package set or from compiler wey you compile yourself.

Real reasons dey to run am: Solaris workload wey you need keep alive, zones deployment wey you already dey operate, or interest to read the source code. The distributions wey we list above dey maintained, and their mailing lists dey answer questions. That one different from making am the default choice for new server.

If na ZFS bring you come here, you no need illumos to get am. Run OpenZFS on Linux or FreeBSD, where dem package, document, and deploy am widely. If you dey consider the BSD side of this same family for server, the practical comparison of Linux and FreeBSD as server platform explain wetin change for daily operation. illumos na where these tools start from, and knowing where dem come from explain plenty about how dem behave, starting with why zpool and zfs feel completely different from the rest of the Linux storage stack.

FAQ

illumos na the same thing as OpenSolaris?

No. OpenSolaris na Sun project and distribution wey Oracle inherit, and Oracle end am for 2010. illumos na separate project wey dem announce on 3 August 2010. Dem build am from the last OpenSolaris core source wey dem publish, the OS/Net consolidation. The first work na to replace the closed binary components wey OpenSolaris ship, including libc_i18n, the NFS lock manager, the cryptographic framework and several drivers. No illumos code come from Oracle after 2010 because Oracle stop publishing am.

Why Linux no fit include ZFS for e kernel?

The licences no fit together. ZFS na CDDL, and the Free Software Foundation classify am as free software licence wey no compatible with GPL. CDDL inherit this incompatibility from MPL 1.1. Linux kernel na GPLv2. The practical result be say OpenZFS on Linux dey ship as out of tree kernel module. Dem usually build am with DKMS against each kernel wey you install, or dem provide am as prebuilt module package. E dey work well, but dem need rebuild the module for every new kernel. So e fit lag behind fresh kernel release by days or weeks.

Oracle Solaris still get support?

Yes. Oracle Solaris 11.4 release on 28 August 2018, and na the current release. Premier Support go reach November 2031, while Extended Support go reach November 2037 under Oracle's lifetime support policy. Oracle lay off most of the Solaris teams on 2 September 2017. Since then, 11.4 don receive support repository updates instead of new major version. Dem no publish the full source the way OpenSolaris publish am.

I fit install illumos for VPS?

Sometimes, but e rare to find am for provider's image list. You generally need provider wey allow you attach custom ISO and use console. Then check say the virtual disk and network drivers for illumos tree recognise the hypervisor devices. OpenIndiana and Tribblix na the usual starting points for general purpose install. SmartOS na for hypervisor host, not guest. Test am for local virtual machine before you pay for anything.

DTrace worth learning if na only Linux I dey use?

The model dey transfer, even though the tool mostly no transfer. Oracle release the DTrace kernel code under GPLv2 for August 2017 and maintain port for Oracle Linux. But dem never merge am into mainline kernel. For Linux, tracing dey run on eBPF in practice. The language bpftrace uses was designed to look like DTrace's D. So probes, predicates and aggregations mean the same thing for both. If you learn the DTrace way of thinking, bpftrace scripts go readable on the first try.