Re: Why fdisk wants the first partition to start at 1 MiB?

[Davidlohr Bueso <dave@gnu.org>]

On Tue, 2012-09-25 at 22:50 +0200, Kay Sievers wrote:
> On Tue, Sep 25, 2012 at 10:33 PM, Francesco Turco <fturco@fastmail.fm> wrote:
> > I'm trying to use fdisk (from util-linux 2.19.1) for creating a
> > partition on a drive. I noticed that the start sector of the first
> > partition must be at least 2048, that is 1 MiB from the beginning of the
> > drive. This can be changed by entering the "expert mode" and using the
> > "move beginning of data in a partition" option. But I'm still wondering
> > why fdisk reserves so much space by default.
> >
> > As far as I know the only sector that should not be used for partitions
> > is the first one, that is, sector 0. It is reserved for the MBR. So the
> > first partition can start at sector 1. I read that the 1 MiB thing is
> > Windows related: http://en.wikipedia.org/wiki/Logical_Disk_Manager. Or
> > it's something that Linux users should also care about? I can't find a
> > convincing explanation anywhere.
> >
> > This 1 MiB thing seems to affect parted, too, as it wants partition
> > boundaries to be multiples of 1 MiB. I don't know if it's related to the
> > problem I have with fdisk, though.
> 
> It's a de-facto standard, which Windows does too. The first megabyte
> is reserved here for a boot loader or any other management data that
> could be needed for a disk or box to boot from.
> 
> Boot loader issues are probably not that interesting on EFI boxes and
> other non-BIOS hardware, but on usually big sized disks it's still a
> safe default.

Right, in fact GPT only reserves 17Kib and the first partition can start
at sector 34, with 512 sector size.

Davidlohr