Quote Originally Posted by MountainX View Post
I do not want this to touch the sda MBR. (As per above, all other OS's are booting perfectly via chainloading.) I only want to get Mythbuntu to boot now (which I believe requires putting grub into sda9).
Any time you run "grub-install" it is going to run several scripts, among which is "grub-setup". This writes to the MBR. I believe the way to make sure it gets written to the partition and not the MBR is to run "grub-setup" directly and using the "--force" option. This is not the devs recommended way of handling things, and if you try putting it on a partition via the "grub-install" command it will complain about it.

The command would be:
grub-setup --force /dev/sda9
Herman's site has a lot more technical information than does this post, and I would advise you to refer to his site for confirmation and a better understanding of how to put GRUB 2 on the partition without also writing to the MBR.

Herman's Illustrated Dual Boot Site:

You can always use the dd command to copy the MBR before you attempt this so you can put it back the way it was if the results aren't what you expected.