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OSX, Extended Partitions, and Logical Partitions


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OSX, Extended Partitions and Logical Partitions


Going straight to the point:

  1. I've been able to install OSX in a primary partition after an extended partition. At least for a few moments only...
  2. I've been able to install OSX in a logical partition. It is functional to some extent.


1) OSX Installed in a Primary Partition After the Extended Partition: A Partial Failure


While trying to install the latest 10.4.8 AMD Test from TPB, I got boot errors with a procedure I had been successfully using in the past. That was bugging me as to why. My target partition was primary, fat32 (type 0xaf), active and before the extended partition. Only later, after some peeking in the MBR and partition table did I notice that nonetheless the target primary partition was after the extended in the partition table.


To make a long story short, I redid my partitioning so that the target partition was not only physically before the extended, but also in the partition table, and from there all went well.


So I thought to myself: maybe then installing osx in a primary after the extended is possible, as long as that target partition is before the extended in the partition table.


I then proceded thusly: starting with a (newly acquired!) drive, only kept a Win install in first partition, then created a fat32/0xaf primary/active at the end of the drive, and then creating an extended+logical in between. Checking the partition table clearly showed the target (d1s2) was before the extended (d1s3) in the table (the logical was d1s5).


I then rebooted on the install dvd and the installation went well. I could even reboot on this active partition to finish the configuration, and there I was with a working OSX in a primary after an extended... I was almost celebrating.


That is until next time I rebooted and there was nothing to get... Checking the partition table, I could see that any details about that partition had been erased there, and the region where I just installed osx was considered unallocated space.

But I could also see with a hex editor that everything was still there, including the boot sector.


So, I then decided to fiddle with the partition table: I just re-entered all the necessary partition information in the table for it (chs begin&end, relative sector, sector number, etc), and upon rebooting, lo and belo OSX started again! Until next reboot of course.


It then appears that the only problem -- although a big one! -- is that OSX(?) decides to erase the partition table entries if it's physically after an extended partition.

So one has to rebuild back that entry every time, which is a bit too much for normal operations, but at least we know a bit more about what is happening.


2) OSX Installed in a Logical Partition: A Partial Success


Next I decided to install OSX in a Logical partition. I had never tried that before, but trusted others' reports that this didn't result in a working OSX.


Well, it doesn't result in a self-sustaining/self-booting OSX system, that's true.


But having a normal OSX install somewhere with a working darwin bootloader, I was able to boot to that logical OSX time after time, without special treatment, and without the HFS+ error.

Using OS Selector or GRUB didn't work, since they can't make this logical partition active before booting (we get the infamous HFS+ error).


/edit: the only special condition that seems to be required is that the logical partition osx is in must be the first logical, at the very beginning of the extended partition. Whenever I placed the logical after another one, however small, I got the usual errors.


As a secondary or tertiary OSX install, this possibility of installing OSX in a Logical partition can be helpful for those with only one PATA HD and short of available primary slots for tests.

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