Am Dienstag 09 Februar 2010 schrieb Mark Pustjens:
On Tue, 9 Feb 2010, Dieter Plaetinck wrote:
On Tue, 9 Feb 2010 20:26:45 +0100 (CET)
Mark Pustjens firstname.lastname@example.org wrote:
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.
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.
Just poked around with grub2 and kvm, you really need the extra space, else it will fail to install. creating partitions with cfdisk will also leave this space.