From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: util-linux-owner@vger.kernel.org Received: from caiajhbdcbhh.dreamhost.com ([208.97.132.177]:59762 "EHLO homiemail-a7.g.dreamhost.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751771Ab2IYVTS (ORCPT ); Tue, 25 Sep 2012 17:19:18 -0400 Message-ID: <1348607954.2531.4.camel@offbook> Subject: Re: Why fdisk wants the first partition to start at 1 MiB? From: Davidlohr Bueso Reply-To: dave@gnu.org To: Kay Sievers Cc: Francesco Turco , util-linux@vger.kernel.org Date: Tue, 25 Sep 2012 23:19:14 +0200 In-Reply-To: References: <1348605188.19630.140661132636721.0CD0D5D4@webmail.messagingengine.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: util-linux-owner@vger.kernel.org List-ID: On Tue, 2012-09-25 at 22:50 +0200, Kay Sievers wrote: > On Tue, Sep 25, 2012 at 10:33 PM, Francesco Turco 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