backtrack iso booting from grub2

[J. Bakshi]

Hello,

As backtrack linux is based on ubuntu, I'm posting this query here.
I'm trying to boot Backtrack 5 iso directly from grub2. I have already
done so with ububtu and debian. Here is the entry for BT5 I have added at grub.cfg

```````````````````````
menuentry "BT-5" {
loopback loop /BT5-KDE-64.iso
linux (loop)/casper/vmlinuz  BOOT=casper boot=casper iso-scan/filename=/BT5-KDE-64.iso  nopersistent noprompt --
initrd (loop)/casper/initrd.gz
}
```````````````````````````

but grub throws errors as

```````````````````````````
error:can't read linux header
error:you need to load linux kernel first
`````````````````````````

Any idea what is missing here ? I have already checked the iso by mounting as loop device
and confirmed the presence of casper/vmlinuz and casper/initrd.gz. So why is it complaining ?

Thanks