initramfs to chroot jail

I am trying to boot Trisquel into a jail with the help of unionfs-fuse. I have been tampering with initramfs scripts and I think it finally combine the two filesystems (/root and /media/tomahawk - this second is the one I mount RW) into /mnt but when I try to

exec run-init /mnt /sbin/init ...

I get mountall: event failed. and the boot process hangs.

My script is as follow:
"this is a fragment just before the end of /usr/share/initramfs-tools/init"

http://pastebin.com/x3UiDEQD

I need your help to continue.