[snip]
With grub2, if you want to troubleshoot update-grub and the resulting
"/boot/grub/grub.cfg", you have to look at "/etc/default/grub",
"/etc/grub.d/*", "/usr/lib/grub/grub-mkconfig_lib", and
"/usr/bin/grub-mkconfig". You might not need to do so often (I haven't
had to do so for my boxes for a very long time) but, if and when you
do, it borders on silly...