Re: Debian and UEFI and GPT
On Thu, Oct 24, 2013 at 9:04 AM, Chris Davies <chris@roaima.co.uk> wrote:
> Andrew M.A. Cater <amacater@galactic.demon.co.uk> wrote:
>>
>> Debian 7.2 runs fine on UEFI, GPT partitioning works fine. You might
>> want to try auto partitioning - there needs to be a 1M space at
>> beginning and end of he disk and a 510M partition marked for EFIboot.
>
> 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?
Disks with msdos and gpt partition tables both have their first
partition start on the 2048th sector; this has nothing to do with the
bios_boot partition that's needed if you use a gpt partition with bios
rather than uefi firmware (a bios_boot partition starts at the 2048th
sector by default).
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.
The EFI System Partition's size must depend on size of the disk to
which it belongs. On my laptop with a 24GB ssd (and 1TB hd for
"/home"), the ESP is 93MB (the ESP has Ubuntu and Fedora grub setups):
[root@lenovo15]# gdisk -l /dev/sda
...
Number Start (sector) End (sector) Size Code Name
1 2048 194559 94.0 MiB EF00
2 194560 46903295 22.3 GiB 8300
[root@lenovo15]# df -h /dev/sda1
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 93M 4.4M 89M 5% /boot/efi
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