Score:0

How to update GRUB in a dual booting disk?

ng flag

I want to install Fedora (I want to use GNOME 40) with Ubuntu 20.04 on my disk. I am afraid of updating GRUB directly with update-grub in Ubuntu than in Fedora will break the bootloader. What is the right way to update the bootloader?

My Disk part table:My disk part table

PonJar avatar
in flag
I know of no reason why updating grub in Ubuntu will break the boot loader of another Linux distribution assuming your Fedora uses grub also. You can update from either distribution and it should just work. If you customise using one distribution and update from the other that customisation will be lost temporarily.
guiverc avatar
cn flag
I use fedora, opensuse, ubuntu on the same drive/box and I'm unaware of any differences with `grub`, likewise debian (but it's a different box). The only difference is the `update-grub` & some easier user-scripts that exist in Ubuntu don't exist in fedora/opensuse/.. (they usually have been added to Debian though)
C.S.Cameron avatar
cn flag
GRUB just boots the OS, it does not alter it. If you are worried back up /boot/grub/grub.cfg before proceeding.
oldfred avatar
cn flag
You may need to add lvm2 driver if Fedora uses LVM for os-prober to find it from Ubuntu. The grub-update only updates menu & does search for other installs. You may need to do grub-install from Ubuntu to make it first in boot order, if Ubuntu is your default boot. Or use efibootmgr to change boot order. see `man efibootmgr`
Score:0
in flag

Never fear! Debian (and, by extension, Ubuntu), includes os-prober in the default configuration for GRUB. That means that simply calling update-grub will update the GRUB installation, and detect any other installed operating systems. Calling it from Ubuntu shouldn't break the Fedora installation.

Note that, by default, update-grub is also called on every update of the grub package, or of the kernel. Unless you have specifically configured GRUB in an unusual way, you will probably not need to update GRUB (if GRUB is installed from Ubuntu, and not in Fedora).

You only need one GRUB install: you could have two disks, with two installs, but that unneeded. GRUB is good at booting almost any other OS: I have a dual boot windows/Debian machine, and Windows boots without ever realizing it isn't the first thing to start after POST.

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