grub2 memdisk config

menuentry "HD firmware update" {
  linux16 /memdisk iso
  initrd16 /fwsh33.iso
}

menuentry "BIOS update" {
  linux16 /memdisk iso
  initrd16 /7wuj39uc.iso
}

mount image

dpavlin@x200:~$ sudo fdisk -l -u /boot/bios.img 
You must set cylinders.
You can do this from the extra functions menu.

Disk /boot/bios.img: 0 MB, 0 bytes
64 heads, 32 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

         Device Boot      Start         End      Blocks   Id  System
/boot/bios.img1   *          32       47103       23536    4  FAT16 <32M

calculate offset

dpavlin@x200:~$ echo '32*512' | bc
16384

and mount it

dpavlin@x200:~$ sudo mount /boot/bios.img /tmp/bios/ -o loop,offset=16384 -t vfat

links

grub2 memdisk config

mount image