Re: [gentoo-user] Re: MBR & GPT dual compliant format

[Neil Bothwick]

On 23 July 2016 04:29:50 CEST, James <wireless@×××××××××××.com> wrote:
> R0b0t1 <r030t1 <at> gmail.com> writes:
>
> > On Jul 22, 2016 5:43 PM, "Neil Bothwick" <neil <at> digimed.co.uk>
> wrote:
> > > I take it this is a limitation of Apple's firmware as I have set
> up a
> > > number of uUEFI systems and never had to do this.
>
> > It is.
>
>
> There is another document that talks in depth about the issue,
> although
> it was centric to using gpt disk on a bios world that was slowly
> moving
> to efi [1].
>
>
> [1] http://mjg59.dreamwidth.org/8035.html
>
> Here is the essence::
> "But most BIOSes (and most older operating systems) don't understand
> GPT, so
> plugging in a GPT-partitioned disk would result in the system
> believing that
> the drive was uninitialised. This is avoided by specifying a
> protective MBR.
> This is a valid MBR partition table with a single partition covering
> the
> entire disk (or the first 2.2TB of the disk if it's larger than that)
> and
> the partition type set to 0xee ("GPT Protective"). GPT-unaware BIOSes
> and
> operating systems will see a partition they don't understand and
> simply
> ignore it."
>
>
> I do not know how to set up a 'protective MBR', that's my issue. This
> reference goes on to talk about how the code was written for parted
> but
> never made the permanent status. It sure would fix a lot of
> installation
> issues among many different distros. An excellent read, if anyone has
> the
> time. Me, I'm going to use this method::
>
> 1. First, write an example of what the partition table should look
> like.
>
> 2. Figure out the separate tools & sequences to achieve the final
> result.
>
> 3. Document the steps so they are clearly available for our community.
>
> 4. Hope that one of the devs/hackers spins a patched version of a
> "parted"
> formatting tool to achieve this ability, system-rescue seems  to be
> the best
> home. Or if a patched parted only lives in an overlay, that would ease
> quite
> a lot of pain for many folks as in my research experience, setting up
> the
> disk partitioning schemes is the toughest part of an installation
> these
> days. This duality of disk usage  is critical to my cluster testing
> schema.
> I'll  also have a variety of bootstap codes to deal with from various
> embedded systems, in addition to commonly purchased hardware
> platforms, so
> extending the formatting to other forms of storage, in a consistent
> and
> generic way, provides an even greater appeal.
>
> From the same doc::
> "It violates the spec and it confuses the majority of partitioning
> tools. I
> wrote some code to make parted do it at one point, but I don't believe
> it
> was ever merged. It's very difficult to make it work well. "
>
> They discuss also some of the MAC family of issues and explain why
> macs
> still suffer from this malaise. I hope that code is still around....
>
>
> Thanks for all the advice and help.
> James

Step 1: Use gdisk to create a 1M partition at the start of the disk. 
Step 2: Set its type to EF02
Step 3: There is no step 3,don't overcomplicate things, all the information you need has already been posted. 

-- 
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