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How can I "isolate" GRUB from one distro to another on a multi-boot setup?

cn flag

I have a triple boot setup with KDE Neon Unstable (we'll call this the primary since that's the one I use the most so far), Ubuntu MATE development release, & Windows 10 on a laptop (thanks to 500GB + 1TB SSDs I can add a few more in the future).

How can I "isolate" GRUB of a non-primary distro (installed on the partition where the distro is installed), and have a "master" GRUB from the primary distro that's install on the disk itself? I'd like to be able to update GRUB on each non-primary distro without screwing the theme and setup of another, especially the primary GRUB.

I was thinking that, similar to how we can boot to Windows Boot Manager from GRUB, I can boot to my Ubuntu MATE's GRUB from my Neon's GRUB if need be.

Edit: I've hit a little snag. I updated my Ubuntu MATE, and forgot to remove GRUB on it. It ended up overwriting my Neon GRUB, but I can't use Neon's GRUB again. I tried update-grub, and reinstalling it but no go.

ar flag
Each SSD can have its own EFI System Partition (ESP). Normally, there is only one ESP in a SSD. If you have two SSD, you can have two ESP and two installations of `grub` pointing to two different ESPs. That said, this will not help if you have three Ubuntu based distros. BTW, KDE Neon is not an [official flavor of Ubuntu](https://ubuntu.com/download/flavours) and therefore off topic here.
oldfred avatar
cn flag
With Ubuntu you do not have to install grub, if other install's grub will boot the Ubuntu install and it should. `sudo ubiquity -b` from live installer in live mode. http://askubuntu.com/questions/838450/how-can-ubiquity-be-forced-not-to-install-grub/838527#838527 I turn off os-prober and add only the boot stanza's want into 40_custom. https://help.ubuntu.com/community/Grub2/CustomMenus
cn flag
@user68186 I'm aware that KDE Neon's considered off-topic, but it's not like it's using GRUB from its own repo. And besides, I have Ubuntu MATE as well.
cn flag
@oldfred so removing OS prober on a non-primary distro will fix it?
ar flag
@oldfred 's idea sounds better than mine. You will have one grub installed by the primary OS. Its OS prober will will pick up the other Ubuntu OS with with no grub.
oldfred avatar
cn flag
I have many Ubuntu installs, and some are obsolete. So my 40_custom allows me to exclude them. But another install when updating grub will make itself as default boot, so I always have to edit /EFI/ubuntu/grub.cfg with my main working install. You can boot main install & just do a grub install, not update to make it default again.
cn flag
So your secondary distros don't have GRUB package at all? I did that similar setup before. It becomes a pain when I need to restart because I would need to fully power off the machine or wait couple of hours. In addition, the recovery options gets overpopulated. I was thinking that, similar to how we can boot to Windows Boot Manager from GRUB, I can boot to my Ubuntu MATE's GRUB from my Neon's GRUB if need be (edited my post to show the scenario I was thinking off).
C.S.Cameron avatar
cn flag
As long as all OS boot UEFI, updating GRUB on Neon should add the rest of the OS to Neon's boot menu.
cn flag
I've hit a little snag. I updated my Ubuntu MATE, and forgot to remove GRUB on it. It ended up overwriting my Neon GRUB, but I can't use it again. I tried `update-grub`, and reinstalling it.
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