imac rev D 7.0 rel booting issue

[Shane Ambler]

Peter Grehan wrote:
> Hi Richard,
> 
>> I installed FreeBSD 7 on partitions 11-16; those begin at 11g.
> ..
>> I seem to remember something about the imacs having an 8g limit.
>> Is this what I am running into?
> 
> I believe this might be the case: it's a limit with OpenFirmware,
> which the FreeBSD loader uses to access disk blocks.

I do believe all the coloured imacs have the 8G limit.

>> Why does it not affect the NB2 installation?
> 
> As you mentioned, the NetBSD kernel is in the os9 partition, which is
> < 8G. Once the o/s has booted, NetBSD (and FreeBSD) will use hardware
> to directly access the drives and
> 
> An issue you have seen is that the FreeBSD loader has no HFS 
> filesystem support, so it can't boot a kernel that is on the same HFS
> partition that it may itself live on.
> 

Even MacOS 9 & X has this issue - you may need to reorganise to get
around it.

The technical side is that "the partition that contains the kernel must
be within the first 8G of the drive".
Once the kernel has started up it can then mount partitions that are
outside the 8G that hold the rest of your software. (This would be up to
120G I think)

With NetBSD booting from the os9 partition the kernel is starting from 
there, once running it can access it's partition that goes outside the 
8G. It's not actually booting from the 10G partition you have for it.

You will need say a <200M partition inside the 8G to hold the FreeBSD 
kernel and /etc to get it started so it can then get to it's main 
partition for the rest. I'm not certain how much more is needed - I 
would normally have /bin /sbin on the root partition but I don't think 
you need them to get things started. You may want them there for 
emergency recovery though.


-- 

Shane Ambler
FreeBSD (at) ShaneWare (dot) Biz

http://ShaneWare.Biz