Re: Debian and UEFI and GPT
On Thu, Oct 24, 2013 at 4:33 PM, Sven Hartge <sven@svenhartge.de> wrote:
> Chris Davies <chris@roaima.co.uk> wrote:
>> Tom H <tomh0665@gmail.com> wrote:
>>> On Thu, Oct 24, 2013 at 9:04 AM, Chris Davies <chris@roaima.co.uk> wrote:
>>>>
>>>> I assume the 1MB space at the beginning is for grub_boot? I found I
>>>> needed that for my big (3TB) GPT disks. What's the space required at
>>>> the end of the disk?
>>>
>>> A gpt disk needs 34 sectors at its beginning; the 0th is the mbr, the
>>> 1st is the gpt header, the 2nd-33rd are for the partition table (for
>>> 128 possible partitions at 128 bytes per partition). And it needs 33
>>> sectors at its end; it's the same as the beginning minus the mbr.
>>>
>> What does it use those sectors at the end for? A duplicate of the ones
>> at the front? If so, do parted and other partitioning tools write to
>> both?
>
> Yes, the sectors at the end are a backup version of the GPT, so if one
> ever accidently overwrite the start of a medium there is always another
> version of the GPT at the end.
>
> All GPT-aware tools must write to both versions and complain of they are
> not in sync.
+1
Unfortunately grub doesn't (yet) fallback to the secondary config:
https://bugzilla.redhat.com/show_bug.cgi?id=1022743
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