Changing Grub’s Default

This took me a while to figure out. Probably because I was using the instructions for BIOS-based instead of UEFI-based machines. Here’s a link to the info (CUSTOMIZING THE GRUB 2 CONFIGURATION FILE), but I’ll lay out the key points below.

First, find the grub config file here: /etc/default/grub. This stores settings for grub. We need to change GRUBDEFAULT. By default the setting is “saved” which means it will use the last kernel installed. If you would like to default to a specific system, list the systems with this command:

awk -F\' '$1=="menuentry " {print $2}' /etc/grub2.cfg

Copy the output of that command to the GRUBDEFAULT setting. Now we need to rebuild grub.cfg.

grub.cfg lives in a different place depending on if you’re on a bios system or a uefi system. Here are the commands for rebuilding grub.cfg:

• On BIOS-based machines, issue the following command as root:

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

• On UEFI-based machines, issue the following command as root:

    grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg
  

  NOTE: Notice how ‘centos’ is defined instead of ‘redhat’

To load the last selected grub entry, make sure these lines are in your grub file: /etc/default/grub

GRUB_DEFAULT="saved"
GRUB_SAVEDEFAULT="true