How do I make sure grub is only installed once?

Question

I currently have Windows on one partition, and Ubuntu on another. I'd like to install Quimo, and possibly Mint and/or Lubuntu as well.

How do I make sure that only Ubuntu has Grub, and that the others don't install it too, or, if more appropriate, make sure that Ubuntu is the only one that is used?

Answer 1

The installation of grub has 2 parts: the resource files, and the boot loader. Each OS installation has its own resource files, but the boot loader is always installed on the master boot record. Effectively, the boot loader that is installed later will overwrite the former. In that sense, you can have only one full functional grub at a time.

I guess the tricky part (and your real question) is, how to make several Os'es work together in a multiboot fashion. This can be done in 2 ways:

The first is to make the main grub installation load the other OS'es. This is done my modifying the grub config (specifically the file /boot/grub/grub.cfg) to include instructions on how to load additional OS'es. On some distributions (I think Ubuntu) this can be done automatically by an OS prober. This method is not very nice, as it requires changes to the main installation every time you upgrade the kernel, but it works.

The second is to make secondary OS'es install their boot loader on a partition rather than the MBR, and tell the main grub installation to chainload the secondary installations. I have a separate question on this (didn't really work for me so please add an answer if you make it). This method is elegant and is my preferred, however setting it up can be tricky depending on your luck.

Answer 2

As a practical answer on how to do what @phunehehe wrote, i would suggest that during the installation precess of the other distros you have a choice (usually under an advanced button) to untick the option to install Grub on the MBR, and hence you can be sure that your current Grub isn't replaced.

But in order to make the Ubuntu's Grub to be aware on the new distros, you have to probe the disk for the other OSs installation with a program like os-prober, that does it automatically for you when you run the sudo grub-mkconfig -o /boot/grub/grub.cfg (of course after backing up the grub.cfg file). and sudo update-grub at the end.

In case it has hard time to find your OSs, you can create custom file (40_custom) and in it point to your other OSs kernel and initrd files, see this ubuntu wiki article about Grub2 it includes all the information you need.