Say Hello to Hexley


What is Darwin?

Darwin is the open source operating system developed by Apple and used as the basis for Mac OS X, as well as OS X on the Apple TV and iPhone.

What's in Darwin?

Darwin includes all of the components of Mac OS X which Apple has decided to release under an open source license, as well as a number of components from third parties which were already open source.

  • The kernel, xnu.
  • A standard set of shells and utilities (called the “BSD subsystem” on Mac OS X, where it an optional component; under Darwin this is a core part of the operating system because Darwin doesn't include the Aqua user interface), including a compiler toolchain.
  • A number of components developed by Apple for Mac OS X, including versions of CoreFoundation, configd, launchd, NetInfo, and Rendezvous.
  • A number of Apple-developed drivers.
  • Apache, MySQL, PHP, and X11.

Does Darwin include a GUI?

While Darwin does include an X server (known as XDarwin), the Apple-released distribution doesn't also provide a desktop environment such as GNOME or KDE, and doesn't provide any window managers besides twm, included as part of X11 itself.

Darwin does not Mac OS X's Aqua user interface, nor does it include Carbon or Cocoa, Mac OS X's application development frameworks.

Who is Hexley?

Hexley is Darwin's mascot, a duck-billed platypus, and was created by Jon Hooper. The name Hexley was actually a mistake: he was supposed to be named after Thomas Henry Huxley, a biologist who was a proponent of Charles Darwin's theories of evolution. By the time the mistake was discovered, it was too late to change it.


Do the components in Darwin differ from those included with Mac OS X?

In many cases, no. For example, although not recommended or supported by Apple, many people developing drivers for Mac OS X run kernels they have built themselves from the Darwin xnu sources.

In some cases, however, there are differences. The version of CoreFoundation included in Darwin is known as “CoreFoundation Lite” (or simply “CFLite”), because it doesn't contain everything that the Mac OS X release of CoreFoundation includes.

In general, it's not recommended that you replace components of a Mac OS X system with those built from source from the Darwin releases, because apart from there being occasional differences in the available functionality, there's a risk of running into version mismatches and core system components may stop working.

What's the Darwin source repository?

The Darwin Source Repository is a project created in 2007 to ensure that the sources to Darwin are always available. Since the closure of the OpenDarwin project, Apple's own site became the only place that Darwin components could be obtained, and this presented a number of problems:

  • Sources governed by the Apple Public Source License required registration with Apple and logging in before they could be downloaded (this is not, however, a requirement of the license—simply a policy decision by Apple), posing difficulty for automated build scripts (especially concerning those components which are easily portable to other operating systems), and anybody wishing to remain anonymous.
  • If Apple decides to stop distributing the sources, there would be no way to obtain them (Apple has already stopped distributing some early releases of Darwin).

To combat these problems, the Darwin Source Repository was created, to ensure that—thanks to the resources of—the Darwin sources are permanently and easily available from mirrors across the world.