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

mike cloaked mike.cloaked at gmail.com
Mon Jul 2 12:26:23 EDT 2012

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)?


mike c

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