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

9 Feb 2010

      On Tue, 9 Feb 2010, Dieter Plaetinck wrote:
...
On Tue, 9 Feb 2010 20:26:45 +0100 (CET)
Mark Pustjens  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