[arch-general] [patch] AIF, partition table compatibility with grub2.

[Mark Pustjens]

On Tue, 9 Feb 2010, Dieter Plaetinck wrote:

> On Tue, 9 Feb 2010 20:26:45 +0100 (CET)
> Mark Pustjens <pustjens at dds.nl> wrote:
>
>> Hi list,
>>
>> The attatched patch adds the `-D' option to the sfdisk call.
>> This causes some extra space to be saved for the MBR, which is needed
>> for grub2 in some cases.
>>
>> Please let me know what you think.
>>
>> Greetings/Groetjes
>>
>> Mark Pustjens
>>
>
> Hi!
> man sfdisk:
>
>       -D or --DOS
>              For DOS-compatibility: waste a little space.  (More
>       precisely: if a partition cannot contain sector 0, e.g. because
>       that is the MBR of the device, or contains the partition table
>       of an extended partition, then sfdisk would make it  start  the
>       next  sector. However,  when this option is given it skips to
>       the start of the next track, wasting for example 33 sectors (in
>       case of 34 sectors/track), just like certain versions of DOS
>       do.)  Certain Disk Managers and boot loaders (such as OSBS, but
>       not LILO or the OS/2 Boot Manager) also live in this empty
>       space, so maybe you want this option if you use one.
>
> I don't really see the point. this wastes some disk space to be
> compatible with old, past-legacy bootloaders and OS'es.
> why exactly would we want this? "some cases" ?

The disc space wasted is about 32K, not realy something to be sad about.
I used the term `some cases', as I do not know what cases these are 
exactly. I have only encountered one so far.

I was installing arch in a VirtualBox machine. Then I wanted to install 
grub2 (and grub2-gfx). They complained they could not install properly, 
unless I chose to use (depreciated) so-called `block lists'.

As it turns out, in my case the part of the bootloader which is normally 
installed in the MBR was too big. Using the -D flag of sfdisk a little 
extra space was left so this part of the bootloader did fit.

As you can understand, grub2 cannot be called legacy.

>
> Dieter
>

Greetings/Groetjes

Mark Pustjens