Re: gpart on macbook air

On Mon, 01 Oct 2012 12:29:02 +0400
From: "Andrey V. Elsukov" <ae_at_FreeBSD.org> wrote:

On 30.09.2012 23:06, Raoul MEGELAS wrote:
>>> When you are deleting a partition, the kernel completely overwrites  the
>>> partition table and PMBR area. You can compare first 34 blocks before
>>> deletion and after to see what is going on.
>> 
>> I can understand that, but i would have thought
>> that the deletion of the concerned partition was written preserving others???
>> 
>> something like:
>> 
>> - read the gpt table
>> - find the offset
>> - zeroes the partition entry
>> - rewrites the table?
>> 
>> is not that logic?
>> 
>> if it is not so, i does not understand this behaviour.
> Hi, Raoul,
>
> The kernel has a copy of the partition table in the memory.
> When you are deleting some partition, it removes the partition entry
> from the memory, constructs updated GPT header and table, calculates
> checksums and writes this data into corresponding places.
> Any way, this should correctly work.
>
> My guess is that Apple's boot loader detects some changes and
> just doesn't want to work. If you think that gpart incorrectly works,
> please make a copy of first 34 blocks before and after deletion and
> send them to me.

Hi Andrey,

thanks for your clear explaination; that make sense.
in all case i will backup my 18g freebsd partition and
and delete it.
as soon as possible will send privately the two copy of the first 
34 blocks of the disk, before and after deletion.

Thanks again.

Raoul
rmgls_at_free.fr