Comment 8 for bug 1017678

Confirming the behaviour stated by axeoth on 2012-09-26.

For some reasons, existing grub.cfg files on other partitions seem to completely fool the update-grub scripts on other partitions (more precise, the linux-boot-order script).

The problem still exists with Xenial Mate uname -a:

Linux xxxxx12 4.4.0-47-generic #68-Ubuntu SMP Wed Oct 26 19:39:52 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Even confirmed, that os-prober gets fooled by a grub.cfg file on a non-system partition that contains a partial backup of a system partition (here: complete directory /boot)!