Install Grub to a HDD image 2767

On Wed, 18 Oct 2006 23:03:13 -0700, Tim

When using the grub shell to setup the loader from a running GNU-Linux, it will accept "device" mappings. This is useful for virtual disks.

The example below shows how to setup the loader on a virtual floppy. Hard disks are similar, but must account for the MBR and individual parbreastion offsets. This can be modelled with two loopbacks (one for the MBR and one for a parbreastion.) But, for the sake of simplicity, I'll try showing the easier case first, a virtual floppy disk. The following example also buttumes the grub "stage" files are installed on the image.

Before starting the grub shell, set the mapping the loop device and virtual floppy.

# losetupdev-loop0 disk.img # grub --no-floppy

#

Watch for any errors after the "setup" command (or any of the commands.)

When modelling virtual hard disks, the virtual disk geometry is important. The MBR is at (0,0,0), and the first parbreastion starts at (0,1,0), where (C,H,S) are (cylinder, head, sector). For example, if your virtual disk is using 63 sectors per track, the offset to the first parbreastion is 32256 bytes.

losetup -o 32256dev-loop1 disk.img

Perhaps, that is enough to get you started. BTW, it has always required extra patience for me to get this right when working with virtual disks. OT: The last "gotcha" for me was the somewhat arbitrary head limit (max head count is 255, not 256.)

-- Douglas Mayne