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frugal technology, simple living and guerrilla large-appliance repair
Sat, 26 Sep 2015

Rebuilding GRUB 2 entries in Fedora 22 for UEFI systems after modifying /etc/default/grub

I'm surprised that the Fedora documentation for working with GRUB 2 doesn't address rebuilding GRUB 2 entries for EFI booting.

They do address it, but they get it wrong.

The grub2-mkconfig instructions for both BIOS and UEFI systems are the same. The problem is that this instruction will only build the BIOS entries. The UEFI entries won't be rebuilt.

Once you have your changes set in /etc/default/grub, here is how to rebuild the GRUB 2 entries for BIOS and UEFI systems?

BIOS systems

# grub2-mkconfig -o /boot/grub2/grub.cfg

UEFI systems

# grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg

It is perfectly OK to do both of these commands (using root, hence the # prompt, or with sudo), but you do need the one that matches your booting method (BIOS for older systems, optionally UEFI for newer systems).

The only reason I figured this out is because I poked around quite a bit when having dual-booting issues. Someone should fix the Fedora GRUB page. I'm a Fedora member and could probably make the fix myself, but I'm not 100 percent sure what I'm doing here is the absolute best method because my GRUB bootlines after doing this look different then they do when the system (either yum or dnf) does a kernel update.