sudo apt-get install grml-rescueboot

@ubuntu-desktop:~/Downloads$ sudo mv raring-desktop-i386.iso /boot/grml/
[sudo] password for : 

@ubuntu-desktop:~/Downloads$ sudo update-grub
Generating grub.cfg ...
Found background image: /usr/share/images/desktop-base/desktop-grub.png
Found linux image: /boot/vmlinuz-3.2.0-36-generic
Found initrd image: /boot/initrd.img-3.2.0-36-generic
Found memtest86+ image: /boot/memtest86+.bin
Found Grml ISO image: /boot/grml/raring-desktop-i386.iso
done

@ubuntu-desktop:/boot/grub$ cat grub.cfg
#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#

### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
  set have_grubenv=true
  load_env
fi
set default="0"
if [ "${prev_saved_entry}" ]; then
  set saved_entry="${prev_saved_entry}"
  save_env saved_entry
  set prev_saved_entry=
  save_env prev_saved_entry
  set boot_once=true
fi

function savedefault {
  if [ -z "${boot_once}" ]; then
    saved_entry="${chosen}"
    save_env saved_entry
  fi
}

function recordfail {
  set recordfail=1
  if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi
}

function load_video {
  insmod vbe
  insmod vga
  insmod video_bochs
  insmod video_cirrus
}

insmod part_msdos
insmod ext2
set root='(hd0,msdos3)'
search --no-floppy --fs-uuid --set=root ae02ece1-192f-4996-8067-144aaa760f93
if loadfont /usr/share/grub/unicode.pf2 ; then
  set gfxmode=auto
  load_video
  insmod gfxterm
  insmod part_msdos
  insmod ext2
  set root='(hd0,msdos3)'
  search --no-floppy --fs-uuid --set=root ae02ece1-192f-4996-8067-144aaa760f93
  set locale_dir=($root)/boot/grub/locale
  set lang=fr_FR
  insmod gettext
fi
terminal_output gfxterm
if [ "${recordfail}" = 1 ]; then
  set timeout=-1
else
  set timeout=4
fi
### END /etc/grub.d/00_header ###

### BEGIN /etc/grub.d/05_debian_theme ###
insmod part_msdos
insmod ext2
set root='(hd0,msdos3)'
search --no-floppy --fs-uuid --set=root ae02ece1-192f-4996-8067-144aaa760f93
insmod png
if background_image /usr/share/images/desktop-base/spacefun-grub.png; then
  set color_normal=light-gray/black
  set color_highlight=white/black
else
  set menu_color_normal=white/black
  set menu_color_highlight=black/light-gray
  if background_color 44,0,30; then
    clear
  fi
fi
### END /etc/grub.d/05_debian_theme ###

### BEGIN /etc/grub.d/10_linux ###
function gfxmode {
	set gfxpayload="${1}"
	if [ "${1}" = "keep" ]; then
		set vt_handoff=vt.handoff=7
	else
		set vt_handoff=
	fi
}
if [ "${recordfail}" != 1 ]; then
  if [ -e ${prefix}/gfxblacklist.txt ]; then
    if hwmatch ${prefix}/gfxblacklist.txt 3; then
      if [ ${match} = 0 ]; then
        set linux_gfx_mode=keep
      else
        set linux_gfx_mode=text
      fi
    else
      set linux_gfx_mode=text
    fi
  else
    set linux_gfx_mode=keep
  fi
else
  set linux_gfx_mode=text
fi
export linux_gfx_mode
if [ "${linux_gfx_mode}" != "text" ]; then load_video; fi
menuentry 'Ubuntu, avec Linux 3.2.0-36-generic' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos3)'
	search --no-floppy --fs-uuid --set=root ae02ece1-192f-4996-8067-144aaa760f93
	linux	/boot/vmlinuz-3.2.0-36-generic root=UUID=ae02ece1-192f-4996-8067-144aaa760f93 ro   quiet splash $vt_handoff
	initrd	/boot/initrd.img-3.2.0-36-generic
}
menuentry 'Ubuntu, avec Linux 3.2.0-36-generic (mode de dépannage)' --class ubuntu --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos3)'
	search --no-floppy --fs-uuid --set=root ae02ece1-192f-4996-8067-144aaa760f93
	echo	'Chargement de Linux 3.2.0-36-generic ...'
	linux	/boot/vmlinuz-3.2.0-36-generic root=UUID=ae02ece1-192f-4996-8067-144aaa760f93 ro recovery nomodeset 
	echo	'Chargement du disque mémoire initial ...'
	initrd	/boot/initrd.img-3.2.0-36-generic
}
### END /etc/grub.d/10_linux ###

### BEGIN /etc/grub.d/20_linux_xen ###
### END /etc/grub.d/20_linux_xen ###

### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" {
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos3)'
	search --no-floppy --fs-uuid --set=root ae02ece1-192f-4996-8067-144aaa760f93
	linux16	/boot/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos3)'
	search --no-floppy --fs-uuid --set=root ae02ece1-192f-4996-8067-144aaa760f93
	linux16	/boot/memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###

### BEGIN /etc/grub.d/30_os-prober ###
### END /etc/grub.d/30_os-prober ###

### BEGIN /etc/grub.d/30_uefi-firmware ###
### END /etc/grub.d/30_uefi-firmware ###

### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###

### BEGIN /etc/grub.d/41_custom ###
if [ -f  $prefix/custom.cfg ]; then
  source $prefix/custom.cfg;
fi
### END /etc/grub.d/41_custom ###

### BEGIN /etc/grub.d/42_grml ###
menuentry "Grml Rescue System (raring-desktop-i386.iso)" {
        insmod part_msdos
        insmod ext2
        set root='(hd0,msdos3)'
        search --no-floppy --fs-uuid --set=root ae02ece1-192f-4996-8067-144aaa760f93
        iso_path="/boot/grml/raring-desktop-i386.iso"
        export iso_path
        kernelopts="   "
        export kernelopts
        loopback loop "/boot/grml/raring-desktop-i386.iso"
        set root=(loop)
        configfile /boot/grub/loopback.cfg
}
### END /etc/grub.d/42_grml ###