In the wishlist item tracked by: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=585563 we taught grub-mkconfig to accept a -t ${TARGET_ROOT} argument which behaves in a similar manner as 'grub-install --root-directory=/target'. We also need to teach some of the helper scripts about this environment variable. The patch proposed in this wishlist item provides the functionality for 10_linux.in so that it functions properly when the user specifies the -t argument to grub-mkconfig.