The nature of kernel of the FreeBSD

[Robert Watson]

On Thu, 7 Sep 2006, Erik Trulsson wrote:

> On Wed, Sep 06, 2006 at 07:20:39PM -0300, Eder wrote:
>> A doubt,
>>
>> Kernel of the FreeBSD is monolithic, correct !!!
>
> Correct.
>
>> The MacOS is derived from kernel of the FreeBSD, correct !!!
>
> Incorrect.  The kernel of MacOS X is mainly derived from the Mach kernel, 
> not from FreeBSD.  I believe it also contains much code from various 
> BSD-derivatives (including FreeBSD) but the basic design is that of Mach 
> rather than that of BSD.

I think that is a poor characterization.  The vast majority of code in the Mac 
OS X kernel is device driver code in IOKit, which is from neither BSD nor 
Mach.  Mach provides the VM and IPC, but it's hrad to argue that the 
architecture of the Mac OS X is the Mach architecture, because it's not a 
micro-kernel , and the kernel does not aspire to be one.  The major 
visible/complex services in the kernel, both file system and network stack, 
are very BSD, and are directly derived from FreeBSD.  I think it's reasonable 
to argue that Mac OS X is significantly influenced, both in architecture and 
code, by both Mach and BSD, but pretty inaccurate to state that it adopts one 
architecture over the other -- it really adopts both.

Robert N M Watson
Computer Laboratory
University of Cambridge