Mac OS underlying FreeBSD - does it run Linux emulation?

Robert Watson rwatson at FreeBSD.org
Wed Apr 4 14:39:04 UTC 2007


On Wed, 4 Apr 2007, Mike Meyer wrote:

> In <20070404130249.GA41671 at kukulies.org>, Christoph P. Kukulies <kuku at kukulies.org> typed:
>> does  anyone know whether one can run Linux applications under the underlying
>> FreeBSD of the MAC OS (on an Intel Core Duo mini Mac)?
>
> No, you can't. The "underlying" FreeBSD is userland code; not kernel code. 
> The OSX kernel is based on Mach.

While it's true you can't run Linux binaries on Mac OS X, it's not for the 
reason you're suggesting, and your statement regarding FreeBSD kernel code in 
Mac OS X is simply incorrect.  The Mac OS X kernel, XNU, contains significant 
quantities of FreeBSD kernel source code, including a FreeBSD-derived VFS and 
network stack.  Other parts of the kernel, such as the scheduler and VM 
system, are derived from Mach.  While the FreeBSD-derived code has been 
significantly modified since it was originally forked, a lot of code moves 
backward and forward between the platforms: the FreeBSD audit subsystem is 
derived from the Mac OS X audit subsystem, and Mac OS X's smbfs and MAC 
Framework support are derived from FreeBSD.

Robert N M Watson
Computer Laboratory
University of Cambridge


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