dual boot – Ubuntu 24.04 booting problems

Welcome to ASK

You might be able to install a new boot loader from the BIOS. This is machine dependent.

If you have a USB with install media you can boot from that and then do the following: –

To find details of your disks: –

sudo fdisk -l

Find the disk with the EFI on it; note the disk sdx (eg sda) and the EFI partition-number. This is the number at the end of sda, for example sda4 would be 4.

Now re-install the missing boot loader using ‘efibootmgr’ as follows: –

efibootmgr -c -d /dev/sdx -p partition-number -L ubuntu -l '\EFI\ubuntu\grubx64.efi'

efibootmgr -c -d /dev/sdx -p partition-number -L ubuntu -l '\EFI\ubuntu\shimx64.efi'

You need to replace sdx with your disk identifier. Quite possibly sda

You need to replace partition-number with the EFI partition number.

For more information and details of how to replace grub see the following link.

https://www.linuxbabe.com/command-line/how-to-use-linux-efibootmgr-examples