[arch-general] A question specifically about upgrading an existing arch system from grub legacy to grub without UEFI or GPT

gt static.vortex at gmx.com
Mon Jul 2 12:39:53 EDT 2012

On Mon, Jul 02, 2012 at 05:26:23PM +0100, mike cloaked wrote:
> I have been following the discussions in various places including on
> this list about the forthcoming change from grub to become grub-legacy
> and the default bootloader becoming grub2.
> On all my arch systems I have grub with MBR partitioning, booting to
> BIOS initially - and none of my systems is modern enough to have UEFI
> instead of BIOS.
> So I have been reading up on what I will need to do when grub2 version
> 2.00 appears in [core] - and how to successfully achieve the
> changeover. However I still cannot determine if it will be "necessary"
> to make sure that there is a post-MBR gap of 2MiB between the MBR and
> the first partition when the system will remain using MBR partitioning
> and grub2 will be the bootloader.  So this applies to systems with no
> GPT partitions, and no UEFI.
> In my systems that have been running some time some have 64 sectors to
> where the start of the first partition is, and others have 2,000
> sectors which is about 1MiB - and I still don't know if grub2 version
> 2.00 will not work on those systems or not.  I do know that other
> distros such as Fedora version F16 have systems running successfully
> using grub2 prior to version 2.00 with MBR partitioning and BIOS and
> boot perfectly well without the 2MiB post MBR gap. Perhaps this
> changes with the release of grub2 version 2.00?
> Achieving a post-MBR gap of at least 2MiB will be a painful process as
> shrinking the first partition and then moving it towards partition 2
> with an MBR partitioned disk is time consuming and not always
> successful in those systems where in the past I have adjusted the
> partitions on a drive. Maybe the recent versions of tools such as
> PartedMagic will cope better than it did a couple of years ago?
> Can someone help out with a clear explanation please.  I am usually
> pretty good with upgrades and preparation but this has foxed me!  i.e.
> specifically for a BIOS-MBR hard drive using grub2 that it is vital to
> have a post-MBR gap of at least 2 MiB (where no GPT partitioning will
> be in use)?

Why do you need to upgrade to grub2? Even if grub-legacy won't be in the
official repositories, it'll be in the AUR. Also, you don't need to
reinstall grub every now and then, so i don't see the need to upgrade.

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