[lug] Mixing Ubuntu and Fedora Bootloaders

[D. Stimits]

Hi,

When dealing with my only computer's bootloader I can get nervous trying to mix Ubuntu's GRUB and Fedora's GRUB2. This mix makes me want to ask and be certain before I "fix" something and make a system unbootable or lose my already correct boot menu.

I have dual boot with an older Fedora 27 and newer Ubuntu 18.04 LTS on "/dev/sda", plus Windows on "/dev/sdb". The partitions are UEFI.

Previously this was all booted through Fedora 27, but I recently updated packages on Ubuntu (perhaps I should just blacklist grub packages on Ubuntu), and the Ubuntu bootloader took over. I already have a customized grub config I want to keep under the F27 bootloader (sda1, "/boot/efi/EFI/fedora/grub.cfg"), and I am wondering if there is a safe way to just load the bootloader binary to once again point to the F27 "/boot" for options without generating a new config which might break or overwrite this old config?

I am used to older BIOS partitions, and and unsure of what the "correct" way is to just put the F27 bootloader back in without overwriting any configurations. I do have all operating systems currently available (I had to edit Ubuntu's Fedora entries), so I don't really need to chroot, I can just boot to Fedora for any grub operations, but for the mix of Ubuntu/grub and Fedora/grub2 and UEFI I get nervous. I don't know if the old grub2-install is still correct, nor do I know how to name partitions correctly when EFI is involved.

Thanks!
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