Modern EC2 instances on AWS boot without invoking initramfs by default. So if you want to do things like repartition your disk, where the root partition is, you’ll be scratching your head why your initramfs hooks aren’t loading.

After an hour or two of debugging, I figured out an easy way to enable it. This is tested on Ubuntu 24.04 LTS:

sudo rm /etc/default/grub.d/40-force-partuuid.cfg
sudo update-grub
sudo grub-mkconfig -o /boot/grub/grub.cfg

# On the next reboot initramfs will run
sudo reboot

Enjoy.