Hi, the decision to stay with the old shell script's command interface was made 2 years ago:
http://lists.gnu.org/archive/html/grub-devel/2014-11/msg00076.html Vladimir 'φ-coder/phcoder' Serbinenko wrote: "I think that old parser is better. The only reason the change happened is that it's a bug that sneaked in during migration to C. It should be fixed." I.e. the correct way to add -J is without preceeding "--". Afaik, this decision was implemented in march 2015: http://git.savannah.gnu.org/cgit/grub.git/commit/?id=cf47a2fba5852014bc59959c5e357e8313933414 "grub-mkrescue: pass all unrecognized options unchanged to xorriso." Have a nice day :) Thomas
