Re: Debian and UEFI and GPT

[Sven Hartge <sven@svenhartge.de>]

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.

Grüße,
S°

-- 
Sigmentation fault. Core dumped.