howto create a bootable livesystem usb stick, which boots iso images with grub2
fdisk -l
mkdir /mnt/usb mount /dev/sdX1 /mnt/usb
grub-install --force --no-floppy --root-directory=/mnt/usb /dev/sdX
edit /mnt/usb/boot/grub/grub.cfg
### MultiBootStick
# grub2 direct ISO boot config
menuentry "ubuntustudio-12.04-dvd-amd64" {
set isofile="/iso/ubuntustudio-12.04-dvd-amd64.iso"
loopback loop $isofile
linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile noeject noprompt --
initrd (loop)/casper/initrd.lz
}
reboot from stick - have fun :)